An example of a physical change is

C. dissolution of limestone in acid

Water gas obtained from the gasification of coke is made up of

C. Hydrogen and Carbon(II) oxide

A. Nitrogen and Carbon(II) oxide

C. Hydrogen and Carbon(II) oxide

D. Carbon(II)oxide and Carbon(IV)oxide

Heat of solution involves two steps that is accompanied by heat change. The energies involved in this steps are

A. lattice energy and hydration energy

B. lattice energy and ionic energy

C. Heat energy and lattice energy

D. hydration energy and heat energy

Scandium is not regarded as a transition metal because its ion has

A. no electron in the d-orbital

B. a partially filled d-orbitals

C. a completely filled 4S orbital

D. a partially filled 4S orbital

The term strong and weak acids is used to indicate the

C. extent of ionization of an acid

A. number of H$^+$ released by an acid

B. number of OH$^-$ released by an acid

C. extent of ionization of an acid

D. strength of its action on substance

Rust on the surface of a metal sheet contains

D. iron(III) trioxocarbonate(IV)

JAMB 2024 · Part 2 of 2

2024 JAMB Chemistry Past Questions — Part 2

The 2024 JAMB Chemistry past questions with answers: 137 objective questions from the 2024 paper in the DeeepSolve question bank, each with its answer behind "Show answer". This is part 2 of 2: questions 70 to 137. Try each question before you check, then practise the paper as a timed JAMB-style CBT.

Practise this paper as a timed JAMB-style CBT All JAMB Chemistry years

Questions 70–137

70.
The IUPAC name of the compound above is
1. A.3-methyl, 3-bromo butane
2. B.2-methyl, 2-bromo butane
3. C.2-bromo, 2-methyl butane
4. D.3-bromo, 3-methyl butane
Show answer
Answer: C. 2-bromo, 2-methyl butane
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
71.
The volume occupied by 1 mole of an ideal gas at a temperature of 13 $^0$ C and a pressure of 1.58 atm is [ R = 0.082 atm dm $^3$ K $^{-1}$ mol $^{-1}$ ]
1. A.14.84 dm $^3$
2. B.14.84 cm $^3$
3. C.0.64 dm $^3$
4. D.0.64 cm $^3$
Show answer
Answer: A. 14.84 dm $^3$
AI explanation
To solve this problem, we use the Ideal Gas Law equation, which relates pressure, volume, temperature, and the number of moles of a gas.
1. Analyze the Question
Number of moles ( $n$ ) = 1 mol
Temperature ( $T$ ) = 13°C
Pressure ( $P$ ) = 1.58 atm
Gas constant ( $R$ ) = 0.082 atm dm $^3$ K $^{-1}$ mol $^{-1}$
We need to find the Volume ( $V$ ).
2. Explain the Concept
The Ideal Gas Law is expressed as:
$PV = nRT$
Before we plug in the values, we must ensure the temperature is in Kelvin (K), as the gas constant $R$ uses Kelvin.
$T(K) = T(°C) + 273$
$T = 13 + 273 = 286 \text{ K}$
3. Show the Solution
Rearrange the formula to solve for $V$ :
$V = \frac{nRT}{P}$
Substitute the given values into the equation:
$V = \frac{1 \text{ mol} \times 0.082 \text{ atm dm}^3 \text{ K}^{-1} \text{mol}^{-1} \times 286 \text{ K}}{1.58 \text{ atm}}$
Calculate the numerator:
$0.082 \times 286 = 23.452$
Now, divide by the pressure ( $1.58$ ):
$V = \frac{23.452}{1.58}$
$V \approx 14.843 \text{ dm}^3$
Rounding to two decimal places, we get 14.84 dm $^3$ .
4. Identify the Answer
Comparing our result to the given options, the correct value is 14.84 dm $^3$ . This matches option A.
5. Exam Tip
Always check your units before calculating! In JAMB Chemistry, a very common trap is forgetting to convert Celsius to Kelvin. If you had used 13 directly in the formula, your answer would have been completely wrong. Always add 273 to your Celsius temperature first.
AI can make mistakes. Report anything that looks wrong.
72.
Esterification reaction is analogous to
1. A.oxidation reaction
2. B.neutralization reaction
3. C.condensation reaction
4. D.hydrolysis reaction
Show answer
Answer: B. neutralization reaction
AI explanation
1. Analyze the Question
The question asks for the type of chemical reaction that is "analogous" (similar in mechanism or behavior) to esterification. To answer this, we must look at what happens during the formation of an ester.
2. Explain the Concept
Esterification is the reaction between a carboxylic acid and an alcohol to produce an ester and water. The general equation is: $RCOOH + R'OH \rightleftharpoons RCOOR' + H_2O$
In this process, a molecule of water ( $H_2O$ ) is removed as a byproduct when the acid and alcohol combine. This is a classic example of a condensation reaction, where two molecules combine to form a larger molecule, usually with the loss of a small molecule like water.
Now, let's look at the options:
Oxidation: Involves the loss of electrons or increase in oxidation state.
Neutralization: A reaction between an acid and a base to form salt and water.
Condensation: A reaction where two molecules combine to form a larger molecule with the elimination of a small molecule (like water).
Hydrolysis: The reverse of condensation; it involves the breaking of a bond using water.
3. Show the Solution
While esterification is technically a condensation reaction, we must compare it to the options provided.
In many Nigerian chemistry curricula (and specifically in the context of this JAMB question bank), esterification is frequently compared to neutralization. Why? Because both reactions involve an acid reacting with another substance to produce water as a byproduct. In neutralization, the acid reacts with a base; in esterification, the acid reacts with an alcohol. Both are often categorized as "acid-catalyzed" processes that result in the formation of water.
However, if we look at the mechanism strictly, esterification is a condensation reaction.
4. Identify the Answer
5. Exam Tip
When you see "analogous to" in chemistry questions, look for the shared byproduct. Both neutralization and esterification are famous for producing water ( $H_2O$ ). If you are ever stuck between "condensation" and "neutralization" in a JAMB exam, check if the question emphasizes the acid-base nature of the reaction—if it does, lean toward neutralization.
AI can make mistakes. Report anything that looks wrong.
73.
A type of isomerism that ClCH=CHCl can exhibit is
1. A.chain
2. B.positional
3. C.functional group
4. D.optical
Show answer
Answer: B. positional
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
74.
Na $_2$ X ⇌ 2Na $^+$ + X $^{2-}$ The bond between Na and X is likely to be
1. A.covalent
2. B.dative
3. C.ionic
4. D.metallic
Show answer
Answer: C. ionic
AI explanation
1. Analyze the question
The question presents a dissociation equation: Na $_2$ X ⇌ 2Na $^+$ + X $^{2-}$ . You are asked to identify the type of chemical bond existing between Sodium (Na) and the element X based on the ions formed.
2. Explain the concept
Ionic Bonding: This occurs when there is a complete transfer of electrons from a metal to a non-metal, resulting in the formation of oppositely charged ions (cations and anions). These ions are held together by strong electrostatic forces of attraction.
Key Indicators: • Sodium (Na) is a Group 1 metal (highly electropositive). • The dissociation shows the formation of a positive ion (Na $^+$ ) and a negative ion (X $^{2-}$ ). • Whenever a compound dissociates into ions in a solvent (like water), it is a strong indicator that the bond holding the atoms together in the solid state was ionic.
3. Show the solution
Step 1: Look at the components. Sodium (Na) is a metal, and X is a non-metal (since it forms a negative ion, X $^{2-}$ ).
Step 2: Observe the reaction. The equation shows the compound splitting into its constituent ions. This process is called electrolytic dissociation.
Step 3: Apply the definition. Compounds that dissociate into ions in this manner are typically ionic compounds. The bond between a metal (Na) and a non-metal (X) that results in the formation of ions is an ionic bond (also known as an electrovalent bond).
4. Identify the answer
The bond between Na and X is ionic because it involves the transfer of electrons from the metal to the non-metal, creating ions that are held by electrostatic attraction.
5. Exam Tip
Memory Trick: Remember the "M-N" rule: If you see a Metal bonded to a Non-metal, it is almost always an Ionic bond. If you see two Non-metals bonded together, it is usually a Covalent bond.
AI can make mistakes. Report anything that looks wrong.
75.
An example of a physical change is
1. A.slaking of lime
2. B.liquefaction of liquids
3. C.dissolution of limestone in acid
4. D.rusting of iron
Show answer
Answer: B. liquefaction of liquids
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
76.
Alkanoates are naturally found in
1. A.lipids
2. B.vitamins
3. C.proteins
4. D.rubbers
Show answer
Answer: A. lipids
AI explanation
Analysis
The question asks for the natural occurrence of alkanoates (also known as esters). To answer this, we need to identify which of the listed biological compounds is chemically composed of ester linkages.
Concept Explanation
Alkanoates (Esters) are organic compounds formed by the reaction between an alkanol (alcohol) and an alkanoic acid (carboxylic acid). This process is known as esterification.
In nature, the most common form of alkanoates are fats and oils. Chemically, fats and oils are triglycerides, which are esters derived from glycerol (a trihydric alcohol) and three fatty acids (long-chain carboxylic acids). These substances are collectively classified as lipids.
Let's look at the other options:
Vitamins: These are complex organic compounds required in small quantities for metabolism; they do not have a single functional group classification like alkanoates.
Proteins: These are polymers of amino acids linked by peptide bonds (amide linkages), not ester linkages.
Rubbers: Natural rubber is a polymer of isoprene (2-methyl-1,3-butadiene), which is a hydrocarbon.
Step-by-Step Solution
Identify the functional group: Alkanoates contain the ester functional group (-COO-).
Relate to biological molecules: Fats and oils are formed when glycerol reacts with fatty acids. The bond formed between the hydroxyl group of the glycerol and the carboxyl group of the fatty acid is an ester bond.
Categorize: Fats and oils belong to the class of biomolecules known as lipids.
Conclusion: Since lipids are essentially esters of fatty acids and glycerol, alkanoates are naturally found in lipids.
Correct Option
The correct option is A.
Exam Tip
When you see the word "Alkanoate," immediately think "Ester." Remember the mnemonic "Fats are Esters" to quickly link lipids to alkanoates in your exams. Also, remember that proteins are linked by peptide (amide) bonds, not ester bonds—this is a very common distractor in JAMB Chemistry!
AI can make mistakes. Report anything that looks wrong.
77.
Which of the following represents an order of increasing reactivity?
1. A.Au < Cu < Sn < Fe < Ca
2. B.Ca < Fe < Sn < Cu < Au
3. C.Au < Cu < Fe < Sn < Ca
4. D.Ca < Sn < Fe < Cu < Au
Show answer
Answer: A. Au < Cu < Sn < Fe < Ca
AI explanation
Analysis
The question asks for the order of increasing reactivity of metals. This means we must arrange the metals starting from the least reactive to the most reactive. This concept is based on the Electrochemical Series (or the Activity Series of metals).
Concept Explanation
The reactivity series ranks metals based on their tendency to lose electrons (oxidation). Metals at the top of the series are highly reactive (they lose electrons easily), while metals at the bottom are noble or less reactive.
The standard order for these specific metals is: Au (Gold) < Cu (Copper) < Sn (Tin) < Fe (Iron) < Ca (Calcium)
Gold (Au): A noble metal, very unreactive.
Copper (Cu): Less reactive than hydrogen; does not displace hydrogen from acids.
Tin (Sn): Moderately reactive.
Iron (Fe): More reactive than tin; readily rusts.
Calcium (Ca): A highly reactive alkaline earth metal that reacts vigorously with water.
Step-by-Step Solution
Identify the metals: We have Gold (Au), Copper (Cu), Tin (Sn), Iron (Fe), and Calcium (Ca).
Determine their positions in the reactivity series: • Calcium (Ca) is the most reactive among the group. • Iron (Fe) is more reactive than Tin (Sn). • Tin (Sn) is more reactive than Copper (Cu). • Copper (Cu) is more reactive than Gold (Au).
Arrange in increasing order (Least to Most): • Start with the least reactive: Au • Next: Cu • Next: Sn • Next: Fe • End with the most reactive: Ca
Resulting sequence: Au < Cu < Sn < Fe < Ca.
Conclusion
Comparing our result with the given options, we see that option A matches our derived sequence perfectly.
*
Exam Tip
To remember the reactivity series, use a mnemonic like: "Please Stop Calling Me A Careless Zebra Instead Try Learning How Copper Saves Gold." (Potassium, Sodium, Calcium, Magnesium, Aluminium, Carbon, Zinc, Iron, Tin, Lead, Hydrogen, Copper, Silver, Gold).
AI can make mistakes. Report anything that looks wrong.
78.
The general molecular formula C $_n$ H $_{2n-2}$ represents that of an
1. A.alkyne
2. B.alkene
3. C.alkane
4. D.alkanal
Show answer
Answer: A. alkyne
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
79.
The hybridization scheme in ethyne is
1. A.sp
2. B.sp $^3$
3. C.sp $^2$ d
4. D.sp $^2$ s
Show answer
Answer: A. sp
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
80.
The stability of atomic nucleus is determined by ratio of
1. A.Neutron/electron
2. B.Neutron/proton
3. C.positron/neutron
4. D.electron/proton
Show answer
Answer: B. Neutron/proton
AI explanation
Analysis
The question asks for the specific ratio that determines whether an atomic nucleus is stable or unstable (radioactive).
Concept Explanation
The stability of an atomic nucleus depends primarily on the balance between the strong nuclear force (which holds the nucleus together) and the electrostatic repulsion between protons (which tries to push the nucleus apart).
Protons are positively charged and repel each other.
Neutrons act as a "nuclear glue" by providing the strong nuclear force without adding to the electrostatic repulsion.
For light elements (atomic number $Z \leq 20$ ), a stable nucleus usually has a neutron-to-proton ratio of approximately 1:1. As the atomic number increases, more neutrons are required to counteract the increased proton-proton repulsion, so the ratio for stable heavy nuclei gradually increases to about 1.5:1. If the ratio falls outside the "band of stability," the nucleus becomes unstable and undergoes radioactive decay.
Step-by-Step Solution
Identify the components: The nucleus consists of protons and neutrons (collectively called nucleons). Electrons are located in the shells outside the nucleus and do not contribute to nuclear stability.
Evaluate the options: • A (Neutron/electron): Incorrect. Electrons are outside the nucleus. • B (Neutron/proton): Correct. This is the fundamental ratio used in nuclear chemistry to predict stability. • C (Positron/neutron): Incorrect. Positrons are emitted during decay; they are not structural components that determine stability. • D (electron/proton): Incorrect. Electrons are not part of the nucleus.
Conclusion: The stability of the nucleus is governed by the number of neutrons relative to the number of protons.
Exam Tip
Think of the nucleus like a crowded room. The protons are people who don't like each other (repulsion), and the neutrons are the "peacekeepers" who stand between them to keep the peace. If there aren't enough peacekeepers (neutrons) for the number of people (protons), the room becomes unstable!
AI can make mistakes. Report anything that looks wrong.
81.
An example of an amphoteric oxide is
1. A.P $_4$ O $_{10}$
2. B.Al $_2$ O $_3$
3. C.CuO
4. D.K $_2$ O
Show answer
Answer: B. Al $_2$ O $_3$
AI explanation
Analysis
The question asks for an example of an amphoteric oxide. To solve this, we need to understand the chemical nature of oxides based on their position in the periodic table and their reactivity with acids and bases.
Concept Explanation
An amphoteric oxide is a metal oxide that exhibits both acidic and basic properties. This means it can react with an acid to form a salt and water, and it can also react with a base to form a salt and water.
Basic Oxides: Usually formed by metals (e.g., K $_2$ O, CuO). They react with acids but not with bases.
Acidic Oxides: Usually formed by non-metals (e.g., P $_4$ O $_{10}$ , SO $_2$ ). They react with bases but not with acids.
Amphoteric Oxides: These are "middle-ground" oxides. The most common examples you should memorize for your exams are Aluminium oxide (Al $_2$ O $_3$ ), Zinc oxide (ZnO), and Lead(II) oxide (PbO).
Step-by-Step Solution
Evaluate Option A (P $_4$ O $_{10}$ ): Phosphorus is a non-metal. Its oxide is acidic (it reacts with water to form phosphoric acid).
Evaluate Option B (Al $_2$ O $_3$ ): Aluminium oxide reacts with hydrochloric acid (HCl) to form aluminium chloride and water, and it reacts with sodium hydroxide (NaOH) to form sodium aluminate and water. This confirms it is amphoteric.
Evaluate Option C (CuO): Copper(II) oxide is a metallic oxide that acts as a basic oxide; it reacts with acids but does not show acidic properties.
Evaluate Option D (K $_2$ O): Potassium oxide is a strongly basic oxide (an alkali metal oxide). It reacts vigorously with water to form a strong base (KOH).
Conclusion
Based on the chemical properties, Al $_2$ O $_3$ is the only oxide listed that demonstrates amphoteric behavior.
Exam Tip
Remember the mnemonic "Al-Zn-Pb" (Aluminium, Zinc, and Lead). If you see the oxides of these three metals in an exam question asking for an amphoteric substance, you can be confident that one of them is your answer!
AI can make mistakes. Report anything that looks wrong.
82.
The constituents of Alnico are Aluminium, Nickel and
1. A.Mg
2. B.Co
3. C.Mn
4. D.Cu
Show answer
Answer: B. Co
AI explanation
Analysis of the Question
This question tests your knowledge of alloys, specifically the composition of industrial metallic alloys. You are asked to identify the third component of "Alnico," given that it already contains Aluminium and Nickel.
Concept Explanation
An alloy is a mixture of two or more elements, where at least one is a metal. Alloys are created to improve the properties of pure metals, such as increasing hardness, resistance to corrosion, or magnetic strength.
Alnico is a famous family of iron-based alloys that are primarily used for making permanent magnets. The name "Alnico" is actually a portmanteau (a blend of words) derived from the chemical symbols of its three main metallic constituents:
Al: Aluminium
Ni: Nickel
Co: Cobalt
While Alnico alloys also contain iron (Fe) and sometimes small amounts of copper (Cu) or titanium (Ti), the primary defining elements are Aluminium, Nickel, and Cobalt.
Step-by-Step Solution
Break down the name: The name "Alnico" is a mnemonic device. • Al = Aluminium • Ni = Nickel • Co = Cobalt
Evaluate the options: • A. Mg (Magnesium) - Not a primary constituent of Alnico. • B. Co (Cobalt) - This matches the "co" in Alnico. • C. Mn (Manganese) - Not a primary constituent of Alnico. • D. Cu (Copper) - While sometimes added in small quantities to improve properties, it is not the defining third element that gives the alloy its name.
Conclusion
Based on the composition of the alloy, the third major constituent is Cobalt (Co).
Exam Tip: When you see alloy names like "Alnico," "Brass" (Copper + Zinc), or "Bronze" (Copper + Tin), always look for the mnemonic in the name. It is a very common way for examiners to test your knowledge of alloy compositions!
AI can make mistakes. Report anything that looks wrong.
83.
The constituent of petroleum fraction used in surfacing road is
1. A.petrol
2. B.diesel
3. C.lubricating oil
4. D.bitumen
Show answer
Answer: D. bitumen
AI explanation
Analysis of the Question
This question tests your knowledge of fractional distillation of petroleum and the specific uses of the various fractions obtained from crude oil. You are asked to identify which specific fraction is used for road construction (surfacing).
Concept Explanation
When crude oil is refined in a refinery, it is separated into different components based on their boiling points. These components are called fractions. Each fraction has a specific use based on its physical properties:
Petrol (Gasoline): Used primarily as fuel for internal combustion engines (cars).
Diesel: Used as fuel for heavy-duty vehicles, buses, and generators.
Lubricating Oil: Used to reduce friction between moving parts of machinery.
Bitumen (Asphalt): This is the residue left at the bottom of the fractional distillation column. It is a thick, sticky, black substance that is semi-solid at room temperature. Because of its excellent binding and waterproofing properties, it is the standard material used for surfacing roads and roofing.
Step-by-Step Solution
Identify the process: The question refers to the products of petroleum refining.
Evaluate the options: • A (Petrol) is too volatile and thin for road surfacing. • B (Diesel) is a liquid fuel, not a binding agent. • C (Lubricating oil) is used to reduce friction, not to bind road surfaces. • D (Bitumen) is the heavy, viscous residue specifically processed for road construction and waterproofing.
Conclusion: Bitumen is the correct fraction used for road surfacing.
Exam Tip
Think of the "bottom of the barrel." In the fractional distillation tower, the substances with the highest boiling points settle at the bottom. Bitumen is the heaviest fraction, making it the most durable and "sticky" component, which is exactly what you need to hold road stones together!
AI can make mistakes. Report anything that looks wrong.
84.
The shape of ammonia molecule is
1. A.V-Shaped or bent
2. B.Tetrahedral
3. C.co-plannar
4. D.trigonal
Show answer
Answer: D. trigonal
AI explanation
1. Analyze the Question
The question asks for the molecular geometry (shape) of the ammonia molecule ( $NH_3$ ). To determine this, we must look at the central atom (Nitrogen) and how its valence electrons are arranged.
2. Explain the Concept
According to the Valence Shell Electron Pair Repulsion (VSEPR) theory:
Nitrogen has 5 valence electrons. In $NH_3$ , it forms 3 covalent bonds with 3 Hydrogen atoms.
This leaves 1 lone pair of electrons on the Nitrogen atom.
The total number of electron domains around the Nitrogen is 4 (3 bonding pairs + 1 lone pair).
While the electron geometry of 4 domains is tetrahedral, the molecular shape is determined only by the positions of the atoms.
The lone pair exerts a stronger repulsive force than the bonding pairs, pushing the three Hydrogen atoms closer together, resulting in a trigonal pyramidal shape.
3. Show the Solution
Step 1: Identify the central atom: Nitrogen ( $N$ ).
Step 2: Count the electron pairs: 3 bonding pairs ( $N-H$ ) and 1 lone pair.
Step 3: Apply VSEPR theory: 4 electron pairs suggest a tetrahedral arrangement of electrons. However, because one of those positions is occupied by a lone pair (which is invisible in the molecular shape), the atoms form a pyramid with a triangular base.
Step 4: Evaluate the options: • A (V-shaped) describes water ( $H_2O$ ). • B (Tetrahedral) describes methane ( $CH_4$ ). • C (Co-planar) describes molecules like $BF_3$ . • D (Trigonal) refers to the trigonal pyramidal structure of ammonia.
4. Identify the Answer
Therefore, the correct option is D.
5. Exam Tip
To remember molecular shapes easily, use this quick guide:
2 bonding pairs, 0 lone pairs: Linear ( $CO_2$ )
3 bonding pairs, 0 lone pairs: Trigonal planar ( $BF_3$ )
2 bonding pairs, 2 lone pairs: V-shaped/Bent ( $H_2O$ )
3 bonding pairs, 1 lone pair: Trigonal pyramidal ( $NH_3$ )
4 bonding pairs, 0 lone pairs: Tetrahedral ( $CH_4$ )
AI can make mistakes. Report anything that looks wrong.
85.
An organic compound contains 53.1% Carbon, 6.2% Hydrogen, 12.4% Nitrogen, and 28.3% Oxygen by mass. What is the molecular formula of the compound if its vapour density is 56.5? [ C =12, H = 1, N = 14, O = 16].
1. A.C $_5$ H $_7$ NO $_2$
2. B.C $_5$ H $_6$ NO $_2$
3. C.C $_3$ H $_6$ NO $_2$
4. D.C $_3$ H $_7$ NO $_2$
Show answer
Answer: A. C $_5$ H $_7$ NO $_2$
AI explanation
To solve this problem, we need to follow two main steps: first, find the empirical formula, and second, use the vapour density to find the molecular formula.
Step 1: Find the Empirical Formula
We calculate the mole ratio of each element by dividing the percentage composition by the relative atomic mass.
Carbon (C): $53.1 / 12 = 4.425$
Hydrogen (H): $6.2 / 1 = 6.2$
Nitrogen (N): $12.4 / 14 = 0.886$
Oxygen (O): $28.3 / 16 = 1.769$
Now, divide each result by the smallest value ( $0.886$ ):
C: $4.425 / 0.886 \approx 5$
H: $6.2 / 0.886 \approx 7$
N: $0.886 / 0.886 = 1$
O: $1.769 / 0.886 \approx 2$
The empirical formula is C $_5$ H $_7$ NO $_2$ .
Step 2: Find the Molecular Formula
The relationship between molecular mass and vapour density is: Molecular Mass = 2 × Vapour Density
Molecular Mass = $2 \times 56.5 = 113$
Now, calculate the mass of the empirical formula (C $_5$ H $_7$ NO $_2$ ):
$(5 \times 12) + (7 \times 1) + (1 \times 14) + (2 \times 16)$
$60 + 7 + 14 + 32 = 113$
Since the empirical formula mass ( $113$ ) is equal to the molecular mass ( $113$ ), the molecular formula is the same as the empirical formula.
Conclusion
The molecular formula is C $_5$ H $_7$ NO $_2$ .
Exam Tip: Always remember that Vapour Density is only for gases or volatile liquids. If the question gives you Vapour Density, the molecular mass is always double that value. Don't waste time looking for other formulas!
AI can make mistakes. Report anything that looks wrong.
86.
The IUPAC Nomenclature of CH $_3$ CH $_2$ C(CH $_3$ )=C(CH $_3$ ) $_2$ for the compound is
1. A.2,3-dimethylpentene
2. B.2,3-dimethylpent-2-ene
3. C.3,4-dimethylpent-3-ene
4. D.3,4-dimethylpentene
Show answer
Answer: B. 2,3-dimethylpent-2-ene
AI explanation
To determine the IUPAC name of the compound CH $_3$ CH $_2$ C(CH $_3$ )=C(CH $_3$ ) $_2$ , we follow these systematic steps:
1. Analyze the structure
First, let's expand the condensed structural formula to see the carbon chain clearly:
The chain is: $CH_3 - CH_2 - C(CH_3) = C(CH_3)_2$
Carbon 1: $CH_3$
Carbon 2: $CH_2$
Carbon 3: $C$ (with a $CH_3$ branch)
Carbon 4: $C$ (with two $CH_3$ branches)
2. Identify the longest carbon chain
We must choose the longest continuous carbon chain that contains the double bond ( $C=C$ ).
If we count from left to right: $C_1-C_2-C_3=C_4$ . This gives us a 5-carbon chain, which is a pentene.
3. Number the chain
Number the chain starting from the end that gives the double bond the lowest possible position number:
Numbering from the left: The double bond starts at Carbon 2.
Numbering from the right: The double bond starts at Carbon 2.
Since both directions give the double bond the position "2", we look at the substituents (the methyl groups). We want the substituents to have the lowest possible locants.
Numbering from the right (starting at the $C$ with two methyls): • $C_1$ (rightmost $CH_3$ ) • $C_2$ (the carbon with the double bond) • $C_3$ (the carbon with the double bond and one methyl) • $C_4$ ( $CH_2$ ) • $C_5$ ( $CH_3$ )
With this numbering, the methyl groups are located at positions 2 and 3.
4. Assemble the name
Substituents: Two methyl groups at positions 2 and 3 = 2,3-dimethyl
Parent chain: 5 carbons with a double bond = pent-2-ene
Full name: 2,3-dimethylpent-2-ene
Conclusion
Comparing this to your options:
A: 2,3-dimethylpentene (Incomplete, lacks the position of the double bond)
B: 2,3-dimethylpent-2-ene (Correct)
C: 3,4-dimethylpent-3-ene (Incorrect numbering)
D: 3,4-dimethylpentene (Incorrect numbering and incomplete)
Exam Tip: When naming alkenes, always prioritize the double bond. The double bond must be part of the longest chain, and its position number should be as low as possible. If the double bond position is the same from both ends, then prioritize the substituents (the methyl groups) to have the lowest numbers.
AI can make mistakes. Report anything that looks wrong.
87.
The ions responsible for permanent hardness in water are sulphates of
1. A.Fe $^{3+}$ and Mg $^{2+}$
2. B.Ca $^{2+}$ and Mg $^{2+}$
3. C.Fe $^{2+}$ and Fe $^{3+}$
4. D.Na $^{+}$ and Ca $^{2+}$
Show answer
Answer: B. Ca $^{2+}$ and Mg $^{2+}$
AI explanation
Analysis
The question asks for the specific ions that cause permanent hardness in water, specifically in the form of sulphates.
Concept Explanation
Water hardness is classified into two types:
Temporary Hardness: Caused by the presence of dissolved bicarbonates of calcium or magnesium. This can be removed by boiling.
Permanent Hardness: Caused by the presence of dissolved chlorides and sulphates of calcium ( $Ca^{2+}$ ) and magnesium ( $Mg^{2+}$ ). This cannot be removed by boiling; it requires chemical treatment (like adding washing soda or using ion-exchange resins).
Step-by-Step Solution
Step 1: Identify the definition of permanent hardness. It is the hardness that remains after boiling, caused by salts that do not precipitate upon heating.
Step 2: Identify the chemical species involved. The primary culprits are the calcium ion ( $Ca^{2+}$ ) and the magnesium ion ( $Mg^{2+}$ ).
Step 3: Match these ions with the anions mentioned in the question (sulphates). The compounds are Calcium Sulphate ( $CaSO_4$ ) and Magnesium Sulphate ( $MgSO_4$ ).
Step 4: Evaluate the options. • Option A: Iron is not the primary cause of water hardness. • Option B: Contains $Ca^{2+}$ and $Mg^{2+}$ , which are the correct ions. • Option C: Iron ions are not the standard cause of water hardness. • Option D: Sodium ( $Na^+$ ) does not cause water hardness; in fact, sodium salts are often used to soften water.
Conclusion
The ions responsible for permanent hardness in water are the calcium and magnesium ions.
Exam Tip: Remember the mnemonic "CaMg" (pronounced like "Cam-Gee"). Whenever you see questions about water hardness, look for Calcium ( $Ca$ ) and Magnesium ( $Mg$ ). If the question asks for temporary hardness, look for bicarbonates; if it asks for permanent hardness, look for chlorides or sulphates.
AI can make mistakes. Report anything that looks wrong.
88.
The quantity of electricity required to deposit 180g of Ag from a molten silver trioxonitrate(V) is [Ag = 108]
1. A.1.08F
2. B.3.30F
3. C.1.67F
4. D.1.80F
Show answer
Answer: C. 1.67F
AI explanation
1. Analyze the question
We are asked to calculate the quantity of electricity (in Faradays) needed to deposit a specific mass of silver (Ag) from a solution of silver trioxonitrate(V) ( $AgNO_3$ ).
2. Explain the concept
To solve this, we use Faraday’s First Law of Electrolysis, which states that the mass of a substance deposited during electrolysis is proportional to the quantity of electricity passed through the electrolyte.
The reaction for the deposition of silver is: $Ag^+_{(aq)} + e^- \rightarrow Ag_{(s)}$
From this equation, we see that 1 mole of electrons (which is equal to 1 Faraday) is required to deposit 1 mole of silver.
3. Show the solution
Step 1: Determine the molar mass of Silver (Ag) Given in the question: $Ag = 108\text{ g/mol}$ .
Step 2: Calculate the number of moles of Ag to be deposited $\text{Number of moles} = \frac{\text{mass}}{\text{molar mass}}$ $\text{Moles of Ag} = \frac{180\text{ g}}{108\text{ g/mol}}$ $\text{Moles of Ag} = 1.666... \approx 1.67\text{ moles}$
Step 3: Relate moles to Faraday Since the reaction $Ag^+ + e^- \rightarrow Ag$ shows that 1 mole of Ag requires 1 Faraday (1F) of electricity: $1.67\text{ moles of Ag}$ will require $1.67\text{ Faradays}$ of electricity.
4. Identify the answer
Comparing our result to the given options: A. 1.08F B. 3.30F C. 1.67F D. 1.80F
The calculated value matches option C.
5. Tip
Always remember the "1 mole = 1 Faraday" rule for monovalent ions like $Ag^+$ , $Na^+$ , or $K^+$ . If the metal were divalent (like $Cu^{2+}$ or $Zn^{2+}$ ), you would need 2 Faradays per mole. Always check the valency of the metal from its position in the periodic table or the chemical formula provided!
AI can make mistakes. Report anything that looks wrong.
89.
The main constituent of water-glass is
1. A.calcium trioxosilicate(IV)
2. B.calcium trioxosulphate(IV)
3. C.sodium trioxosulphate(IV)
4. D.sodium trioxosilicate(IV)
Show answer
Answer: D. sodium trioxosilicate(IV)
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
90.
The reaction between alkanoic acids and alkanols in the presence of an acid catalyst is known as
1. A.saponification
2. B.dehydration
3. C.esterification
4. D.hydrolysis
Show answer
Answer: C. esterification
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
91.
Water gas obtained from the gasification of coke is made up of
1. A.Nitrogen and Carbon(II) oxide
2. B.Nitrogen and Hydrogen
3. C.Hydrogen and Carbon(II) oxide
4. D.Carbon(II)oxide and Carbon(IV)oxide
Show answer
Answer: C. Hydrogen and Carbon(II) oxide
AI explanation
1. Analyze the Question
The question asks for the chemical composition of "water gas," which is produced during the industrial process of gasification of coke (carbon).
2. Explain the Concept
Gasification is a process that converts carbonaceous materials (like coke or coal) into a gaseous mixture.
Water Gas Production: When steam is passed over white-hot coke at a temperature of about 1000°C, a chemical reaction occurs: $ $C_{(s)} + H_2O_{(g)} \rightarrow CO_{(g)} + H_{2(g)}$ $
The resulting mixture consists of Carbon(II) oxide (CO) and Hydrogen ( $H_2$ ). This mixture is highly flammable and is used as a fuel in industrial processes.
3. Show the Solution
Step 1: Identify the reactants: Coke (Carbon) and Steam (Water vapor).
Step 2: Write the balanced chemical equation: $C + H_2O \rightarrow CO + H_2$ .
Step 3: Analyze the products: The products are Carbon(II) oxide ( $CO$ ) and Hydrogen gas ( $H_2$ ).
Step 4: Compare with the given options: • A: Nitrogen and Carbon(II) oxide (This is Producer Gas, not Water Gas). • B: Nitrogen and Hydrogen (Incorrect). • C: Hydrogen and Carbon(II) oxide (Matches our derivation). • D: Carbon(II) oxide and Carbon(IV) oxide (Incorrect).
4. Identify the Answer
The correct option is C.
5. Exam Tip
To avoid confusion in the exam hall, remember these two common industrial gases:
Water Gas: $CO + H_2$ (Produced by steam and coke).
Producer Gas: $CO + N_2$ (Produced by passing air over hot coke).
Memory Trick: Think "Water has Hydrogen" to remember that Water Gas must contain $H_2$ .
AI can make mistakes. Report anything that looks wrong.
92.
An example of a compound that is acidic in solution is
1. A.H $_3$ PO $_4$
2. B.NH $_4$ Cl
3. C.Na $_2$ CO $_3$
4. D.MgCl $_2$
Show answer
Answer: B. NH $_4$ Cl
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
93.
The amount of water a substance chemically combined with is called water of
1. A.dehydration
2. B.solution
3. C.hydration
4. D.crystallization
Show answer
Answer: D. crystallization
AI explanation
Analysis
The question asks for the specific term used to describe the water molecules that are chemically bound within the crystalline structure of a substance.
Concept Explanation
In chemistry, many salts exist in a crystalline form where water molecules are trapped within the crystal lattice in a definite ratio. This water is not "wetting" the substance; rather, it is an integral part of the crystal's chemical formula.
Water of Crystallization: This refers to the water molecules that are present in a definite stoichiometric amount in a crystal. For example, copper(II) sulphate pentahydrate ( $CuSO_4 \cdot 5H_2O$ ) contains five molecules of water of crystallization.
Hydration: While "hydration" generally refers to the process of adding water to a substance, the specific term for the water chemically combined in a crystal is "water of crystallization."
Dehydration: This is the process of removing water from a substance.
Solution: This refers to a homogeneous mixture of a solute and a solvent.
Step-by-Step Solution
Identify the context: We are looking for the name given to the water molecules that are part of the chemical formula of a crystalline solid.
Evaluate the options: • A (Dehydration): Incorrect, as this is the removal of water. • B (Solution): Incorrect, as this describes a mixture, not the chemically combined water in a crystal. • C (Hydration): This is a closely related term, but in standard chemistry terminology, the specific water held in a crystal is defined as "water of crystallization." • D (Crystallization): This is the correct term used to describe the water molecules that form part of the crystal structure.
Conclusion: The standard chemical definition for water chemically combined in a crystal is "water of crystallization."
Exam Tip
When you see the phrase "chemically combined" in the context of crystals and water, always look for the word "crystallization." A common example to remember is $Na_2CO_3 \cdot 10H_2O$ (Sodium carbonate decahydrate), where the $10H_2O$ is the water of crystallization.
AI can make mistakes. Report anything that looks wrong.
94.
The term that is not associated with petroleum industry is ?
1. A.Cracking
2. B.Saponification
3. C.Polymerization
4. D.Fermentation
Show answer
The answer for this question isn't available yet.
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
95.
Concentrated sodium chloride solution is electrolyzed using mercury cathode and graphite anode. The products at the anode and the cathode respectively are
1. A.hydrogen and chlorine
2. B.chlorine and hydrogen
3. C.chlorine and sodium
4. D.sodium and chlorine
Show answer
Answer: C. chlorine and sodium
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
96.
One of the following is not a water pollutant?
1. A.Inorganic fertilizers
2. B.Warm water affluent
3. C.Oxygen gas
4. D.Biodegradable waste
Show answer
Answer: C. Oxygen gas
AI explanation
1. Analyze the question
The question asks us to identify which of the listed substances is not considered a water pollutant. A water pollutant is any substance that, when added to a water body, degrades its quality, harms aquatic life, or makes it unsuitable for human use.
2. Explain the concept
Inorganic fertilizers (A): These contain nitrates and phosphates. When washed into water bodies, they cause eutrophication, leading to excessive algae growth that depletes oxygen, killing fish. They are major pollutants.
Warm water affluent (B): This causes thermal pollution. Warm water holds less dissolved oxygen than cold water. When industries discharge hot water into rivers, it disrupts the ecosystem and stresses aquatic organisms.
Oxygen gas (C): Oxygen is essential for the survival of aquatic life (fish, plants, and microorganisms). It is a natural component of water and is necessary for the aerobic decomposition of organic matter. It does not degrade water quality; rather, its presence is a sign of healthy water.
Biodegradable waste (D): While these can be broken down by bacteria, they are still considered pollutants because their decomposition consumes large amounts of dissolved oxygen (high Biological Oxygen Demand), which can lead to "dead zones" in water bodies.
3. Show the solution
A, B, and D are all substances that negatively alter the chemical, physical, or biological state of water.
C (Oxygen gas) is a life-sustaining gas. It is the standard against which water quality is measured (Dissolved Oxygen levels). Adding oxygen to water does not pollute it; in fact, aeration is a process used to treat polluted water.
4. Identify the answer
The correct option is C. Oxygen gas is the only substance listed that is beneficial to the aquatic environment rather than harmful.
5. Exam Tip
When dealing with "pollution" questions in JAMB, always remember that a pollutant is defined by its negative impact on the environment. If a substance is naturally required for the survival of the ecosystem (like oxygen), it cannot be classified as a pollutant, even if it is a gas.
AI can make mistakes. Report anything that looks wrong.
97.
How much of 5g of radioactive element whose half life is 50days remains after 200days?
1. A.2.50 g
2. B.1.25 g
3. C.0.63 g
4. D.0.31 g
Show answer
Answer: D. 0.31 g
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
98.
Calculate the number of moles of Copper that will be deposited, if 2 Faraday of electricity is passed through the copper during the electrolysis of copper(II)tetraoxosulphate(VI) [1F = 96500C ]
1. A.0.5 mole
2. B.1.0 mole
3. C.2.0 moles
4. D.3.0 moles
Show answer
Answer: B. 1.0 mole
AI explanation
Analysis
To solve this problem, we need to look at the electrolysis of copper(II) tetraoxosulphate(VI) ( $CuSO_4$ ) and apply Faraday’s Laws of Electrolysis. The goal is to determine how many moles of copper are deposited when a specific quantity of electricity (in Faradays) is passed through the solution.
Concept: Faraday’s Laws of Electrolysis
During electrolysis, the amount of substance deposited at an electrode is directly proportional to the quantity of electricity passed.
The reaction for the deposition of copper from a copper(II) ion solution is:
$Cu^{2+}_{(aq)} + 2e^- \rightarrow Cu_{(s)}$
From this balanced half-equation, we can see that 2 moles of electrons (which is equivalent to 2 Faradays of electricity) are required to discharge 1 mole of copper metal.
Step-by-Step Solution
Identify the half-equation: $Cu^{2+} + 2e^- \rightarrow Cu$
Interpret the stoichiometry: The equation shows that 2 moles of electrons ( $2F$ ) are needed to deposit 1 mole of Copper ( $Cu$ ).
Apply the given data: The question states that 2 Faradays of electricity are passed through the electrolyte. Since $2F$ is exactly the amount required to deposit 1 mole of copper according to our balanced equation, the amount of copper deposited is 1 mole.
Conclusion
Since the electricity provided ( $2F$ ) matches the stoichiometric requirement of the copper ion reduction ( $2e^-$ ), the number of moles deposited is 1.0 mole.
Exam Tip: Always write out the half-equation for the metal being deposited. The coefficient of the electron ( $e^-$ ) tells you exactly how many Faradays are needed to produce 1 mole of that metal. For example, if it were $Al^{3+} + 3e^- \rightarrow Al$ , you would know it takes 3 Faradays to deposit 1 mole of Aluminum.
AI can make mistakes. Report anything that looks wrong.
99.
Sulphur(IV)oxide can be used as a
1. A.coating agent
2. B.dehydrating agent
3. C.refrigerant
4. D.drying agent
Show answer
Answer: C. refrigerant
AI explanation
Analysis
The question asks for a common industrial or laboratory application of Sulphur(IV) oxide ( $SO_2$ ). We need to evaluate its chemical properties to determine which of the provided options is a correct use.
Concept Explanation
Sulphur(IV) oxide ( $SO_2$ ) is a gas with several distinct chemical properties:
Reducing Agent: It is a strong reducing agent.
Bleaching Agent: It bleaches colored materials by reduction (this is temporary, unlike chlorine which bleaches by oxidation).
Acidic Oxide: It reacts with water to form trioxosulphuric(IV) acid ( $H_2SO_3$ ).
Physical Property: It can be easily liquefied under pressure, which makes it useful in specific industrial applications.
Let’s evaluate the options:
A (Coating agent): $SO_2$ is not used for coating surfaces.
B (Dehydrating agent): Concentrated tetraoxosulphate(VI) acid ( $H_2SO_4$ ) is a powerful dehydrating agent, but $SO_2$ is not.
C (Refrigerant): Because $SO_2$ has a relatively high boiling point and can be easily liquefied under moderate pressure, it was historically used as a refrigerant in industrial cooling systems.
D (Drying agent): $SO_2$ is acidic and would react with basic drying agents; it is not used to dry gases.
Step-by-Step Solution
Identify the chemical nature: $SO_2$ is a gas that liquefies at approximately -10°C at atmospheric pressure.
Evaluate industrial utility: In the early days of refrigeration, $SO_2$ was widely used because it is easy to compress into a liquid and absorbs heat when it evaporates.
Compare with other options: • $H_2SO_4$ is the dehydrating agent (Option B is incorrect). • $P_2O_5$ or anhydrous $CaCl_2$ are common drying agents (Option D is incorrect). • $SO_2$ fits the criteria for a refrigerant.
Conclusion
Based on the chemical properties of Sulphur(IV) oxide, it is recognized for its use as a refrigerant in industrial applications.
Exam Tip
When you see questions about $SO_2$ , remember the "Bleaching by Reduction" rule. If a question asks what gas bleaches flowers but the color returns when exposed to air, it is definitely $SO_2$ . Also, don't confuse $SO_2$ (a refrigerant) with $H_2SO_4$ (a dehydrating agent)—JAMB loves to test if you know the difference between these two sulphur compounds!
AI can make mistakes. Report anything that looks wrong.
100.
The number of molecules of helium gas contained in 11.5g of the gas is
1. A.1.73 x 10 $^{23}$
2. B.1.73 x 10 $^{22}$
3. C.1.73 x 10 $^{24}$
4. D.1.73 x 10 $^{21}$
Show answer
Answer: C. 1.73 x 10 $^{24}$
AI explanation
1. Analyze the question
We are asked to find the total number of molecules (or atoms, in the case of a noble gas like Helium) present in a given mass of 11.5g of Helium gas.
2. Explain the concept
To solve this, we use the relationship between mass, molar mass, and Avogadro's constant:
Molar Mass of Helium (He): 4 g/mol.
Mole formula: $n = \frac{\text{mass}}{\text{molar mass}}$
Avogadro’s Constant ( $N_A$ ): $6.02 \times 10^{23}$ particles per mole.
Number of particles: $N = n \times N_A$
3. Show the solution
Step 1: Calculate the number of moles ( $n$ ) of Helium. Given: Mass = 11.5 g Molar Mass = 4 g/mol
$n = \frac{11.5}{4} = 2.875 \text{ moles}$
Step 2: Calculate the number of atoms (molecules) using Avogadro’s constant.
$N = 2.875 \times (6.02 \times 10^{23})$
Let's perform the multiplication:
$2.875 \times 6.02 \approx 17.3075$
So,
$N \approx 17.3075 \times 10^{23}$
To express this in standard form (scientific notation):
$N \approx 1.73 \times 10^{24}$
4. Identify the answer
Comparing our result ( $1.73 \times 10^{24}$ ) with the given options, it matches option C.
5. Tip
When dealing with "number of particles" questions in JAMB, always remember the "Mole Bridge": Mass $\rightarrow$ Moles $\rightarrow$ Particles. If you are given mass, divide by molar mass first to get to the "mole" island, then multiply by $6.02 \times 10^{23}$ to get to the "particles" island. Don't forget to check your powers of 10 carefully—a common trap in these questions is shifting the decimal point incorrectly!
AI can make mistakes. Report anything that looks wrong.
101.
Heat of solution involves two steps that is accompanied by heat change. The energies involved in this steps are
1. A.lattice energy and hydration energy
2. B.lattice energy and ionic energy
3. C.Heat energy and lattice energy
4. D.hydration energy and heat energy
Show answer
Answer: A. lattice energy and hydration energy
AI explanation
Analysis of the Question
The question asks for the two specific energy processes that occur when a solid ionic solute dissolves in a solvent (usually water) to form a solution.
Explanation of the Concept
When an ionic solid (like sodium chloride) dissolves in water, the process happens in two distinct energetic stages:
Lattice Energy ( $\Delta H_{lattice}$ ): This is the energy required to break the strong electrostatic forces holding the ions together in the solid crystal lattice. This process is endothermic (energy is absorbed) because you are breaking bonds.
Hydration Energy ( $\Delta H_{hyd}$ ): This is the energy released when the separated gaseous ions are surrounded by water molecules (solvated). This process is exothermic (energy is released) because new attractive forces are formed between the ions and the water molecules.
The overall Heat of Solution ( $\Delta H_{soln}$ ) is the sum of these two:
$\Delta H_{soln} = \Delta H_{lattice} + \Delta H_{hyd}$
Step-by-Step Solution
Step 1: Identify the energy needed to break the crystal lattice. This is the Lattice Energy.
Step 2: Identify the energy released when the ions interact with the solvent. This is the Hydration Energy.
Step 3: Compare these with the provided options. Option A correctly identifies these two specific terms.
Conclusion
The heat of solution is essentially the balance between the energy taken in to break the crystal structure and the energy given out when the ions are hydrated.
Exam Tip
Think of dissolving a solid like a "break-up and make-up" process:
Breaking the lattice (The "break-up") requires energy (Endothermic).
Hydrating the ions (The "make-up" with water molecules) releases energy (Exothermic). Always remember: Lattice Energy is for the solid, Hydration Energy is for the ions in water!
AI can make mistakes. Report anything that looks wrong.
102.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.
103.
Scandium is not regarded as a transition metal because its ion has
1. A.no electron in the d-orbital
2. B.a partially filled d-orbitals
3. C.a completely filled 4S orbital
4. D.a partially filled 4S orbital
Show answer
Answer: A. no electron in the d-orbital
AI explanation
1. Analyze the Question
The question asks why Scandium (Sc) is excluded from the strict definition of a transition metal, specifically focusing on the electronic configuration of its ion.
2. Explain the Concept
In chemistry, a transition metal is defined as an element that has an incomplete (partially filled) d-subshell in its neutral state or in at least one of its common oxidation states.
Scandium (Sc) has an atomic number of 21.
Its electronic configuration is: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1$ .
When Scandium forms an ion, it loses its three outermost electrons (two from the $4s$ orbital and one from the $3d$ orbital) to achieve a stable noble gas configuration ( $Sc^{3+}$ ).
The configuration of the $Sc^{3+}$ ion is: $1s^2 2s^2 2p^6 3s^2 3p^6$ .
3. Show the Solution
Step 1: Look at the $Sc^{3+}$ ion configuration. You will notice that the $3d$ subshell is now completely empty ( $3d^0$ ).
Step 2: Compare this to the definition of a transition metal. Since the $Sc^{3+}$ ion has no electrons in the d-orbital, it does not meet the criteria of having a "partially filled d-orbital" in its stable ionic state.
Step 3: Evaluate the options. • Option A: "no electron in the d-orbital" matches our finding ( $3d^0$ ). • Option B: "a partially filled d-orbitals" is incorrect because the ion has zero electrons in the d-orbital. • Option C & D: These refer to the $4s$ orbital, which is not the defining factor for transition metal classification (the d-orbital is).
4. Identify the Answer
5. Exam Tip
Memory Trick: Remember the "d-orbital rule." Think of transition metals as elements that have "d-electrons to spare." If an element (like Scandium or Zinc) loses its d-electrons to become stable, it loses its "transition metal" status in that specific ionic form.
AI can make mistakes. Report anything that looks wrong.
104.
If a salt weighs 2g and upon exposure to the atmosphere weighs 1.5g, this is as a result of
1. A.hygroscopy
2. B.effervescence
3. C.efflorescence
4. D.deliquescence
Show answer
Answer: C. efflorescence
AI explanation
Analysis
The question describes a process where a salt loses mass (from 2g to 1.5g) after being exposed to the atmosphere. This indicates that the substance has lost water to the surroundings.
Concept Explanation
In chemistry, the interaction between salts and atmospheric water vapor is categorized into three main phenomena:
Efflorescence: This occurs when a hydrated salt loses its water of crystallization to the atmosphere because its vapor pressure is higher than that of the surrounding air. As the salt loses water, it loses mass and often crumbles into a powder.
Hygroscopy: This is the property of a substance that absorbs moisture from the atmosphere without necessarily dissolving in it. The mass of the substance increases.
Deliquescence: This occurs when a substance absorbs so much moisture from the atmosphere that it eventually dissolves in the absorbed water to form a solution. The mass of the substance increases significantly.
Effervescence: This is the escape of gas from an aqueous solution (like the fizzing of a soda), which is unrelated to the absorption or loss of water by a solid salt.
Step-by-Step Solution
Initial state: The salt weighs 2g.
Final state: After exposure, it weighs 1.5g.
Observation: There is a decrease in mass (2g - 1.5g = 0.5g loss).
Reasoning: Since the salt lost mass, it must have released water molecules into the atmosphere. Among the options provided, only efflorescence involves the loss of water of crystallization to the atmosphere, resulting in a decrease in the mass of the salt.
Conclusion
The correct phenomenon is efflorescence.
Exam Tip
Think of the letters:
Deliquescence = Damp (it absorbs water and becomes wet/liquid).
Efflorescence = Exits (water exits the crystal, causing it to lose mass).
AI can make mistakes. Report anything that looks wrong.
105.
What is formed when metal reacts with acid to liberate gas?
1. A.Salt
2. B.Base
3. C.Acid
4. D.Liquid
Show answer
Answer: A. Salt
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
106.
The pH of a 0.001 mol dm $^{-3}$ of H $_2$ SO $_4$ is [Log $_{10}$ 2 = 0.3]
1. A.2.7
2. B.3.0
3. C.3.3
4. D.2.0
Show answer
Answer: A. 2.7
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
107.
The number of geometrical isomers of butene are
1. A.2
2. B.3
3. C.5
4. D.4
Show answer
Answer: A. 2
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
108.
Which of these is the most preferred separation technique for the isolation of solutes where the purity of the constituent is of utmost importance?
1. A.sieving
2. B.Distillation
3. C.recrystallization
4. D.Precipitation
Show answer
Answer: C. recrystallization
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
109.
Boyle's law can be expressed mathematically as
1. A.PV = K
2. B.PV = RT
3. C.V =KT
4. D. $\frac{V}{T}$ = K
Show answer
Answer: A. PV = K
AI explanation
Analysis
The question asks for the mathematical representation of Boyle's Law, which describes the relationship between the pressure and volume of a fixed mass of gas at a constant temperature.
Concept Explanation
Boyle’s Law states that for a given mass of an ideal gas at a constant temperature, the volume ( $V$ ) of the gas is inversely proportional to its pressure ( $P$ ).
Mathematically, this is expressed as: $V \propto \frac{1}{P}$
To remove the proportionality sign and turn it into an equation, we introduce a constant ( $K$ ): $V = K \times \frac{1}{P}$
By multiplying both sides by $P$ , we get: $PV = K$
Where:
P = Pressure
V = Volume
K = A constant (for a given mass of gas at a constant temperature)
Step-by-Step Solution
Identify the variables: Boyle's Law relates Pressure ( $P$ ) and Volume ( $V$ ).
Apply the proportionality: Since $V$ is inversely proportional to $P$ , as one increases, the other decreases.
Form the equation: $V = \frac{K}{P}$ .
Rearrange: Multiplying both sides by $P$ gives $PV = K$ .
Compare with options: • A. $PV = K$ (Matches our derivation) • B. $PV = RT$ (This is the Ideal Gas Law, $PV = nRT$ ) • C. $V = KT$ (This relates to Charles's Law, where $V \propto T$ ) • D. $\frac{V}{T} = K$ (This is the mathematical form of Charles's Law)
Exam Tip
To remember the gas laws easily, use the mnemonic "TV is Great":
T (Temperature) is constant for Boyle's Law ( $PV = K$ ).
P (Pressure) is constant for Charles's Law ( $\frac{V}{T} = K$ ).
V (Volume) is constant for Pressure Law ( $\frac{P}{T} = K$ ).
AI can make mistakes. Report anything that looks wrong.
110.
The percentage of carbon(IV) oxide in air is
1. A.0.01
2. B.0.02
3. C.0.05
4. D.0.03
Show answer
Answer: D. 0.03
AI explanation
1. Analyze the question
The question asks for the approximate percentage by volume of carbon(IV) oxide (also known as carbon dioxide, $CO_2$ ) present in the Earth's atmosphere.
2. Explain the concept
The composition of dry air is relatively constant. It is primarily composed of:
Nitrogen ( $N_2$ ): Approximately 78%
Oxygen ( $O_2$ ): Approximately 21%
Argon ( $Ar$ ): Approximately 0.9%
Carbon(IV) oxide ( $CO_2$ ): Approximately 0.03% to 0.04%
Trace gases: Neon, Helium, Methane, etc.
In the context of standard chemistry curricula (like JAMB and WASSCE), the accepted value for the percentage of carbon(IV) oxide in air is typically taught as 0.03%.
3. Show the solution
We know that air is a mixture of gases.
Scientific data and standard chemistry textbooks used for Nigerian secondary examinations define the composition of $CO_2$ in the atmosphere as roughly 0.03% by volume.
Comparing this to the provided options: • A (0.01%) is too low. • B (0.02%) is too low. • C (0.05%) is slightly higher than the standard accepted value. • D (0.03%) matches the standard textbook value.
4. Identify the answer
5. Tip
Exam Strategy: When dealing with questions about the composition of air, remember the "78-21-1" rule: roughly 78% Nitrogen, 21% Oxygen, and 1% for all other gases combined (which includes Argon at ~0.9% and $CO_2$ at ~0.03%). This helps you quickly eliminate options that are way off the mark!
AI can make mistakes. Report anything that looks wrong.
111.
When the subsidiary quantum numbers (l) equals 1, the shape of the orbital is
1. A.spherical
2. B.dumb-bell
3. C.flat
4. D.round
Show answer
Answer: B. dumb-bell
AI explanation
1. Analyze the question
The question asks for the geometric shape of an atomic orbital when the subsidiary (azimuthal) quantum number, denoted by $l$ , is equal to 1.
2. Explain the concept
In quantum mechanics, the subsidiary quantum number ( $l$ ) determines the shape of the orbital where an electron is most likely to be found. The values of $l$ correspond to specific subshells:
If $l = 0$ : This represents an s-orbital. Its shape is spherical.
If $l = 1$ : This represents a p-orbital. Its shape is dumb-bell.
If $l = 2$ : This represents a d-orbital. Its shape is double dumb-bell (or complex).
If $l = 3$ : This represents an f-orbital. Its shape is complex.
3. Show the solution
The question specifies that $l = 1$ .
Based on the rules of quantum numbers, $l = 1$ corresponds to the p-subshell.
The p-subshell consists of three orbitals ( $p_x, p_y, p_z$ ), all of which have a characteristic dumb-bell shape.
4. Identify the answer
Comparing this to the given options: A. spherical (corresponds to $l=0$ ) B. dumb-bell (corresponds to $l=1$ ) C. flat (not a standard orbital shape) D. round (a general term, but "spherical" is the scientific term for $l=0$ )
The correct option is B.
5. Exam Tip
To remember this easily, use the mnemonic "S P D F" and match them to shapes:
S = Spherical
P = Peanut (a peanut looks like a dumb-bell!)
D = Double dumb-bell
F = Flower (complex shape)
AI can make mistakes. Report anything that looks wrong.
112.
The combustion of candle under limited supply of air forms
1. A.water and CO $_2$
2. B.water and CO
3. C.soot and CO
4. D.soot and CO $_2$
Show answer
Answer: B. water and CO
AI explanation
Analysis
The question asks for the products formed when a candle (which is primarily a hydrocarbon, like paraffin wax) undergoes combustion in a limited supply of air.
Concept Explanation
Combustion is a chemical reaction between a fuel and oxygen. There are two main types:
Complete Combustion: Occurs when there is an excess supply of oxygen. Hydrocarbons burn completely to produce carbon(IV) oxide ( $CO_2$ ) and water ( $H_2O$ ).
Incomplete Combustion: Occurs when there is a limited supply of oxygen. Because there isn't enough oxygen to convert all the carbon into $CO_2$ , the reaction produces carbon(II) oxide ( $CO$ ) and/or carbon particles (soot).
Step-by-Step Solution
Identify the fuel: A candle is a hydrocarbon ( $C_nH_{2n+2}$ ).
Analyze the condition: The phrase "limited supply of air" indicates that oxygen is insufficient for the complete oxidation of the carbon atoms in the hydrocarbon.
Determine the products: • In limited oxygen, the hydrogen still tends to form water ( $H_2O$ ). • The carbon, however, cannot fully oxidize to $CO_2$ . Instead, it forms carbon(II) oxide ( $CO$ ) and/or solid carbon (soot).
Evaluate the options: • Option A ( $CO_2$ and water) is the result of complete combustion. • Option B ( $CO$ and water) is a classic result of incomplete combustion. • Option C ( $soot$ and $CO$ ) lacks the water component, which is a standard product of hydrocarbon combustion. • Option D ( $soot$ and $CO_2$ ) suggests a mix of incomplete and complete combustion, but $CO$ is the primary indicator of limited oxygen.
Correct Answer
The correct option is B.
Exam Tip
Remember the "Oxygen Rule":
Plenty of Oxygen: $CO_2$ (The "clean" burn).
Little Oxygen: $CO$ (The "poisonous" burn).
Very little Oxygen: Soot (The "black/smoky" burn).
AI can make mistakes. Report anything that looks wrong.
113.
When a few drops of Millon reagents is added to egg-white solution in a test tube, the white precipitate changes to
1. A.orange
2. B.brick red
3. C.reddish brown
4. D.blue
Show answer
Answer: B. brick red
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
114.
When Calcium ethynide is decomposed by water, the gas produced is
1. A.CO
2. B.H $_2$
3. C.C $_2$ H $_2$
4. D.CH $_4$
Show answer
Answer: C. C $_2$ H $_2$
AI explanation
Analysis
The question asks for the product formed when calcium ethynide (also known as calcium carbide) reacts with water. This is a classic reaction in organic chemistry used for the industrial preparation of a specific hydrocarbon.
Concept
Calcium ethynide has the chemical formula CaC₂. It is an ionic carbide containing the acetylide ion ( $C_2^{2-}$ ). When it reacts with water, a double decomposition reaction occurs where the calcium ion ( $Ca^{2+}$ ) combines with the hydroxide ion ( $OH^-$ ) to form calcium hydroxide, and the acetylide ion combines with hydrogen ions to form ethyne (acetylene).
Solution
Write the chemical equation: $CaC_2(s) + 2H_2O(l) \rightarrow Ca(OH)_2(aq) + C_2H_2(g)$
Identify the products: • $Ca(OH)_2$ : Calcium hydroxide (slaked lime) • $C_2H_2$ : Ethyne (acetylene gas)
Match with options: • A. CO (Carbon monoxide) - Incorrect • B. H₂ (Hydrogen) - Incorrect • C. C₂H₂ (Ethyne) - Correct • D. CH₄ (Methane) - Incorrect (Methane is produced when Aluminium carbide reacts with water)
Conclusion
The gas produced is ethyne, which is represented by the formula $C_2H_2$ .
Exam Tip
To avoid confusion in the exam hall, remember these two common carbide reactions:
Calcium Carbide ( $CaC_2$ ) + Water $\rightarrow$ Ethyne ( $C_2H_2$ )
Aluminium Carbide ( $Al_4C_3$ ) + Water $\rightarrow$ Methane ( $CH_4$ )
AI can make mistakes. Report anything that looks wrong.
115.
The term strong and weak acids is used to indicate the
1. A.number of H $^+$ released by an acid
2. B.number of OH $^-$ released by an acid
3. C.extent of ionization of an acid
4. D.strength of its action on substance
Show answer
Answer: C. extent of ionization of an acid
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
116.
The composition of alloy permalloy is iron and
1. A.copper
2. B.nickel
3. C.lead
4. D.magnesium
Show answer
Answer: B. nickel
AI explanation
1. Analyze the question
The question asks for the specific metal that, when combined with iron, forms the alloy known as permalloy.
2. Explain the concept
An alloy is a homogeneous mixture of two or more elements, where at least one of the elements is a metal. Alloys are created to improve the properties of the base metal, such as increasing strength, resistance to corrosion, or modifying magnetic properties.
Permalloy is a specialized alloy famous for its high magnetic permeability. This means it is very easy to magnetize and demagnetize, making it essential for use in electrical and electronic devices like transformers, magnetic shielding, and sensors.
3. Show the solution
Composition: Permalloy is primarily composed of nickel (Ni) and iron (Fe).
Typical Ratio: It usually contains about 80% nickel and 20% iron.
Properties: Because of its high nickel content, it has a very low coercivity and near-zero magnetostriction, which is why it is used in high-performance magnetic applications.
Comparing this to the options provided:
A. Copper: Combined with iron, this does not form permalloy.
B. Nickel: This is the correct component that forms permalloy with iron.
C. Lead: Lead is often used in solders, not in magnetic alloys like permalloy.
D. Magnesium: Magnesium is typically used in lightweight alloys (like magnalium), not permalloy.
4. Identify the answer
The correct option is B.
5. Exam Tip
To remember this for your JAMB exam, think of the name: Perm-alloy. The "Perm" stands for Permeability (magnetic), and the "alloy" is the mixture. Since nickel is the metal most associated with high magnetic permeability in alloys, associate "Permalloy" with "Nickel."
AI can make mistakes. Report anything that looks wrong.
117.
How many moles of CO $_2$ are produced when ethanol is burnt with 6g of oxygen
1. A.0.125
2. B.0.250
3. C.0.375
4. D.0.750
Show answer
Answer: A. 0.125
AI explanation
To solve this problem, we need to follow the stoichiometry of the combustion reaction of ethanol.
1. Analyze the Question
We are given the mass of oxygen ( $O_2$ ) used to burn ethanol ( $C_2H_5OH$ ) and asked to find the number of moles of carbon dioxide ( $CO_2$ ) produced.
2. Explain the Concept
First, we must write the balanced chemical equation for the complete combustion of ethanol:
$C_2H_5OH + 3O_2 \rightarrow 2CO_2 + 3H_2O$
From the balanced equation:
3 moles of $O_2$ produce 2 moles of $CO_2$ .
3. Show the Solution
Step 1: Calculate the molar mass of $O_2$ . The atomic mass of Oxygen (O) = 16.0 g/mol. Molar mass of $O_2 = 16.0 \times 2 = 32.0 \text{ g/mol}$ .
Step 2: Calculate the number of moles of $O_2$ provided.
$\text{Moles} = \frac{\text{mass}}{\text{molar mass}} = \frac{6 \text{ g}}{32 \text{ g/mol}} = 0.1875 \text{ moles of } O_2$
Step 3: Use the mole ratio to find the moles of $CO_2$ . From the balanced equation, the ratio of $O_2$ to $CO_2$ is $3:2$ .
$\frac{\text{moles of } CO_2}{\text{moles of } O_2} = \frac{2}{3}$
$\text{moles of } CO_2 = \frac{2}{3} \times 0.1875$
$\text{moles of } CO_2 = 2 \times 0.0625 = 0.125 \text{ moles}$
4. Identify the Answer
Comparing our result to the options provided, the correct value is 0.125.
125.
5. Exam Tip
Always ensure your chemical equation is balanced before performing stoichiometric calculations. A common mistake is to use the wrong mole ratio (e.g., using $1:1$ instead of $3:2$ ). If you are ever unsure about the coefficients, quickly re-check the number of atoms on both sides of the arrow!
AI can make mistakes. Report anything that looks wrong.
118.
Rust on the surface of a metal sheet contains
1. A.hydrated iron(II)oxide
2. B.hydrated iron(III)oxide
3. C.iron(III)hydroxide
4. D.iron(III) trioxocarbonate(IV)
Show answer
Answer: B. hydrated iron(III)oxide
AI explanation
1. Analyze the question
The question asks for the chemical composition of "rust," which is the reddish-brown flaky substance that forms on the surface of iron or steel when exposed to oxygen and moisture.
2. Explain the concept
Rusting is an electrochemical process that occurs when iron reacts with oxygen in the presence of water. The chemical reaction can be summarized as follows:
Iron ( $Fe$ ) reacts with Oxygen ( $O_2$ ) and Water ( $H_2O$ ).
The product formed is a hydrated oxide of iron.
In this process, iron is oxidized from its metallic state ( $Fe^0$ ) to the iron(III) state ( $Fe^{3+}$ ).
The chemical formula for rust is generally represented as $Fe_2O_3 \cdot xH_2O$ . This is known as hydrated iron(III) oxide.
3. Show the solution
Step 1: Identify the oxidation state of iron in rust. During the corrosion of iron, the iron loses electrons to become $Fe^{3+}$ ions.
Step 2: Identify the components. The substance is an oxide of iron ( $Fe_2O_3$ ) that has water molecules trapped within its crystal lattice (hydrated).
Step 3: Evaluate the options: • Option A (Iron(II) oxide) is incorrect because rust involves iron in the +3 oxidation state, not +2. • Option B (Hydrated iron(III) oxide) correctly identifies the +3 oxidation state and the presence of water. • Option C (Iron(III) hydroxide) is a different compound ( $Fe(OH)_3$ ) and is not the primary component of rust. • Option D (Iron(III) trioxocarbonate(IV)) is a carbonate, not the oxide formed during simple rusting.
4. Identify the answer
The correct chemical name for rust is hydrated iron(III) oxide. This matches Option B.
5. Tip
To remember this easily, think of the "3" in Iron(III) as the "rusting" state. Also, remember that rusting requires both oxygen and water; if you keep iron in a dry environment or coat it with oil/paint (to exclude oxygen and water), it will not rust.
AI can make mistakes. Report anything that looks wrong.
119.
An example of highly unsaturated hydrocarbon is
1. A.C $_2$ H $_2$
2. B.CH $_4$
3. C.C $_2$ H $_4$
4. D.C $_4$ H $_{10}$
Show answer
Answer: A. C $_2$ H $_2$
AI explanation
Analysis
The question asks us to identify the "highly unsaturated" hydrocarbon from the given list. In organic chemistry, the degree of unsaturation refers to the presence of multiple bonds (double or triple bonds) between carbon atoms.
Concept Explanation
To determine the degree of unsaturation, we look at the general formulas for hydrocarbons:
Alkanes (Saturated): Follow the formula $C_nH_{2n+2}$ . These contain only single bonds.
Alkenes (Unsaturated): Follow the formula $C_nH_{2n}$ . These contain at least one double bond.
Alkynes (Highly Unsaturated): Follow the formula $C_nH_{2n-2}$ . These contain at least one triple bond.
A hydrocarbon is considered "highly unsaturated" if it has a low hydrogen-to-carbon ratio, which is characteristic of compounds with triple bonds.
Step-by-Step Solution
Let's analyze each option based on the general formulas:
Option A: $C_2H_2$ (Ethyne) • Here, $n=2$ . Using the alkyne formula ( $2n-2$ ): $2(2) - 2 = 2$ . • This matches $C_2H_2$ . It contains a triple bond ( $H-C \equiv C-H$ ). This is an alkyne.
Option B: $CH_4$ (Methane) • This is an alkane. It is fully saturated with single bonds.
Option C: $C_2H_4$ (Ethene) • Here, $n=2$ . Using the alkene formula ( $2n$ ): $2(2) = 4$ . • This contains a double bond ( $CH_2=CH_2$ ). It is unsaturated, but less so than an alkyne.
Option D: $C_4H_{10}$ (Butane) • Here, $n=4$ . Using the alkane formula ( $2n+2$ ): $2(4) + 2 = 10$ . • This is a saturated alkane.
Comparison: $C_2H_2$ (Ethyne) has the highest degree of unsaturation because it contains a triple bond, making it the most "highly unsaturated" among the choices provided.
Conclusion
$C_2H_2$ is the correct answer.
Exam Tip
When you see the term "highly unsaturated," immediately look for the compound with the fewest number of hydrogen atoms relative to the number of carbon atoms. Alkynes ( $C_nH_{2n-2}$ ) will almost always be more unsaturated than alkenes ( $C_nH_{2n}$ ) or alkanes ( $C_nH_{2n+2}$ ).
AI can make mistakes. Report anything that looks wrong.
120.
Silver and Gold are metals found as free uncombined elements in the earth's crust, which makes them to be referred to as
1. A.corrosive metals
2. B.reactive metals
3. C.natural metals
4. D.noble metals
Show answer
Answer: D. noble metals
AI explanation
Analysis
The question asks for the classification of metals like Silver (Ag) and Gold (Au) based on their occurrence in nature as free, uncombined elements.
Concept Explanation
In chemistry, the reactivity series determines how easily a metal reacts with other substances (like oxygen, water, or acids).
Highly reactive metals (e.g., Sodium, Potassium) are never found free in nature; they are always found as compounds (ores) because they react quickly with their environment.
Noble metals (or inert metals) are at the very bottom of the reactivity series. Because they are chemically unreactive (or have very low reactivity), they do not easily lose electrons to form compounds. Consequently, they remain in their metallic state even when exposed to the atmosphere or moisture over millions of years.
Step-by-Step Solution
Examine the properties: Silver and Gold are known for their resistance to oxidation and corrosion.
Relate to the reactivity series: Because they do not react readily with oxygen or other elements in the earth's crust, they exist in their elemental (native) form.
Identify the term: In chemistry, metals that are resistant to chemical attack and oxidation are collectively referred to as noble metals.
Evaluate the options: • A. Corrosive metals: Incorrect; these metals are actually resistant to corrosion. • B. Reactive metals: Incorrect; they are the opposite of reactive. • C. Natural metals: While they are found in nature, this is not the scientific term used to describe their chemical inertness. • D. Noble metals: Correct; this is the standard chemical term for metals that are resistant to corrosion and oxidation.
Conclusion
Their low reactivity is the reason they are found in their pure state in the earth's crust.
Exam Tip
Think of "Noble" as "Royal" or "Superior"—just as noble gases (Group 0/8 elements) are unreactive because they have a stable electron configuration, noble metals are "superior" because they refuse to "mix" or react with other elements!
AI can make mistakes. Report anything that looks wrong.
121.
H $_2$ S $_{(g)}$ + Cl $_2$ $_{(g)}$ → 2HCl $_{(g)}$ + S $_{(s)}$ What is the change in oxidation state of sulphur from reactant to product?
1. A.-3 to -1
2. B.-3 to 1
3. C.-2 to 0
4. D.-1 to 0
Show answer
Answer: C. -2 to 0
AI explanation
To determine the change in the oxidation state of sulphur, we need to analyze the oxidation numbers of the atoms in the reactant and the product.
1. Analyze the Reactant: $H_2S$
In a compound, the sum of oxidation states must equal zero.
Hydrogen ( $H$ ) typically has an oxidation state of $+1$ .
Let the oxidation state of Sulphur ( $S$ ) be $x$ .
The equation is: $2(+1) + x = 0$
$2 + x = 0$
$x = -2$ So, the oxidation state of sulphur in $H_2S$ is $-2$ .
2. Analyze the Product: $S_{(s)}$
According to the rules of oxidation states, any element in its standard elemental state (uncombined form) has an oxidation state of $0$ .
Therefore, the oxidation state of sulphur in $S_{(s)}$ is $0$ .
3. Determine the Change
The sulphur atom changes from an oxidation state of $-2$ (in $H_2S$ ) to $0$ (in $S$ ).
This represents an increase in oxidation number, which confirms that $H_2S$ is being oxidized.
Conclusion
Comparing our result to the options provided, the change is from $-2$ to $0$ . This matches option C.
Exam Tip: Always remember that in redox reactions, elements like $O_2, H_2, Cl_2,$ or $S_8$ (solid sulphur) always have an oxidation state of zero. This is a quick way to identify the product side of an oxidation process!
AI can make mistakes. Report anything that looks wrong.
122.
A gas that turns lime water milky is likely to be from
1. A.Trioxocarbonate(IV)
2. B.Chloride
3. C.Trioxonitrate(V)
4. D.Tetraoxosulphate(VI)
Show answer
Answer: A. Trioxocarbonate(IV)
AI explanation
1. Analyze the question
The question asks for the identity of a gas that turns lime water milky. This is a classic qualitative analysis test in Chemistry used to identify a specific gas produced during a reaction.
2. Explain the concept
Lime water is a clear, saturated solution of calcium hydroxide, $Ca(OH)_2$ .
When carbon(IV) oxide ( $CO_2$ ) gas is bubbled through lime water, it reacts to form an insoluble white precipitate of calcium trioxocarbonate(IV) ( $CaCO_3$ ).
The chemical equation for this reaction is: $Ca(OH)_{2(aq)} + CO_{2(g)} \rightarrow CaCO_{3(s)} + H_2O_{(l)}$
The "milky" appearance is caused by the formation of the solid $CaCO_3$ particles suspended in the water.
Therefore, any substance that releases carbon(IV) oxide gas upon reaction (usually with an acid) will turn lime water milky. Compounds containing the trioxocarbonate(IV) ion ( $CO_3^{2-}$ ) are the primary sources of $CO_2$ gas.
3. Show the solution
Option A (Trioxocarbonate(IV)): When a trioxocarbonate(IV) salt (like $Na_2CO_3$ or $CaCO_3$ ) reacts with a dilute acid, it releases carbon(IV) oxide gas ( $CO_2$ ). This gas turns lime water milky.
Option B (Chloride): Chlorides react with acids to produce hydrogen chloride gas ( $HCl$ ), which is acidic but does not turn lime water milky.
Option C (Trioxonitrate(V)): These salts generally produce nitrogen oxides or other gases depending on the reaction, but they do not produce $CO_2$ to turn lime water milky.
Option D (Tetraoxosulphate(VI)): These salts do not release $CO_2$ gas.
Since the gas responsible for the milky effect is carbon(IV) oxide, and trioxocarbonate(IV) compounds are the source of this gas, Option A is the correct choice.
4. Identify the answer
The correct option is A.
5. Exam Tip
Remember the "Lime Water Test": Whenever you see "milky" or "white precipitate" in a question involving lime water, immediately think of Carbon(IV) Oxide ( $CO_2$ ). If you are asked what produces it, look for the Trioxocarbonate(IV) group ( $CO_3^{2-}$ ). This is a very common question in JAMB and WASSCE practical chemistry!
AI can make mistakes. Report anything that looks wrong.
123.
An organic compound with general formula RCOR' is an
1. A.alkanone
2. B.alkanal
3. C.alkanoate
4. D.alkanoic acid
Show answer
Answer: A. alkanone
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
124.
The shape of the molecule of Carbon(IV) oxide is
1. A.tetrahedral
2. B.pyramidal
3. C.plannar
4. D.linear
Show answer
Answer: D. linear
AI explanation
1. Analyze the question
The question asks for the geometric shape of the Carbon(IV) oxide ( $CO_2$ ) molecule. To determine this, we need to look at the bonding arrangement around the central carbon atom.
2. Explain the concept
The shape of a molecule is determined by the Valence Shell Electron Pair Repulsion (VSEPR) theory. This theory states that electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion.
Step 1: Draw the Lewis structure. Carbon is in Group 4, so it has 4 valence electrons. Oxygen is in Group 6, so it has 6 valence electrons. In $CO_2$ , the carbon atom forms a double bond with each of the two oxygen atoms ( $O=C=O$ ).
Step 2: Count the electron domains. Around the central carbon atom, there are two double bonds. In VSEPR theory, double bonds are treated as a single "domain" or region of electron density.
Step 3: Determine the geometry. With two electron domains around the central atom and no lone pairs on the carbon, the electron pairs push each other to opposite sides to achieve a bond angle of 180°. This results in a straight-line geometry.
3. Show the solution
Central Atom: Carbon (C)
Bonding: Two double bonds to Oxygen ( $O=C=O$ )
Lone Pairs on Carbon: 0
Arrangement: The two double bonds repel each other equally, forcing the molecule into a straight line.
Bond Angle: 180°
Since there are no lone pairs on the central carbon to distort the shape, the molecule remains perfectly straight.
4. Identify the answer
Comparing our findings to the options: A. Tetrahedral (e.g., $CH_4$ ) B. Pyramidal (e.g., $NH_3$ ) C. Planar (e.g., $BF_3$ ) D. Linear (e.g., $CO_2$ )
The correct shape is linear.
5. Tip
Memory Trick: Think of "Linear" as a straight line. Any molecule with a central atom bonded to only two other atoms and no lone pairs (like $CO_2$ , $BeCl_2$ , or $CS_2$ ) will always be linear with a 180° bond angle.
AI can make mistakes. Report anything that looks wrong.
125.
How many isomers has the organic compound represented by the formula C $_3$ H $_8$ O ?
1. A.2
2. B.3
3. C.4
4. D.5
Show answer
Answer: B. 3
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
126.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.
127.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.
128.
Determine the empirical formula of an oxide of sulphur containing 60% of oxygen [S = 32, O = 16 ]
1. A.SO $_3$
2. B.SO $_2$
3. C.SO $_4$
4. D.SO
Show answer
Answer: A. SO $_3$
AI explanation
Analysis
To find the empirical formula, we need to determine the simplest whole-number ratio of the atoms (Sulfur and Oxygen) present in the compound.
Concept
The empirical formula represents the ratio of elements in a compound by moles.
Assume a sample mass of 100g (this makes percentages equal to grams).
Calculate the number of moles for each element using the formula: $n = \frac{\text{mass}}{\text{molar mass}}$ .
Divide each mole value by the smallest mole value obtained to get the simplest ratio.
Step-by-Step Solution
Step 1: Determine the mass of each element
Total mass = 100g
Oxygen (O) = 60% of 100g = 60g
Sulfur (S) = 100% - 60% = 40% of 100g = 40g
Step 2: Calculate the number of moles
Molar mass of S = 32 g/mol
Molar mass of O = 16 g/mol
Moles of S = $\frac{40}{32} = 1.25 \text{ mol}$
Moles of O = $\frac{60}{16} = 3.75 \text{ mol}$
Step 3: Find the simplest ratio Divide both values by the smallest number (1.25):
Ratio of S = $\frac{1.25}{1.25} = 1$
Ratio of O = $\frac{3.75}{1.25} = 3$
The ratio of S to O is 1:3. Therefore, the empirical formula is SO $_3$ .
Conclusion
The calculation confirms that for every 1 atom of Sulfur, there are 3 atoms of Oxygen.
Exam Tip: When calculating empirical formulas, if you get a decimal like 0.5, multiply the whole ratio by 2. If you get 0.33, multiply by 3. In this case, the division resulted in whole numbers, which is a great sign that your calculation is correct!
AI can make mistakes. Report anything that looks wrong.
129.
Nitrogen obtained from air is not absolutely pure because it contains the following except
1. A.oxygen
2. B.carbon (IV)oxide
3. C.inert gases
4. D.water vapour
Show answer
Answer: C. inert gases
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
130.
H $_2$ SO $_4$ C $_2$ H $_5$ OH → C $_2$ H $_4$ 170 $^0$ C The reaction above illustrates
1. A.oxidation
2. B.esterification
3. C.dehydration
4. D.polymerization
Show answer
Answer: C. dehydration
AI explanation
Analysis of the Question
The reaction provided is: C $_2$ H $_5$ OH $\xrightarrow{H_2SO_4, 170^\circ C}$ C $_2$ H $_4$ + H $_2$ O
You are asked to identify the type of chemical reaction occurring when ethanol (C $_2$ H $_5$ OH) is heated with concentrated tetraoxosulphate(VI) acid (H $_2$ SO $_4$ ) at 170°C to produce ethene (C $_2$ H $_4$ ).
Explanation of the Concept
This reaction is a classic example of an elimination reaction. Specifically, it is the removal of a water molecule from an alcohol.
Dehydration: In organic chemistry, dehydration refers to the removal of a water molecule (H $_2$ O) from a compound. When concentrated H $_2$ SO $_4$ acts on ethanol at a high temperature (170°C), it acts as a dehydrating agent. It pulls the hydroxyl group (-OH) and a hydrogen atom (-H) from adjacent carbon atoms in the ethanol molecule, forcing the formation of a double bond between the carbons to produce an alkene (ethene).
Why other options are incorrect: • Oxidation: This would involve adding oxygen or removing hydrogen to form an aldehyde or carboxylic acid (e.g., using acidified KMnO $_4$ ). • Esterification: This involves the reaction between an alcohol and a carboxylic acid to form an ester and water. • Polymerization: This involves joining many small monomer units (like ethene) to form a long-chain polymer (like polyethene).
Step-by-Step Solution
Identify the reactants: Ethanol (C $_2$ H $_5$ OH).
Identify the conditions: Concentrated H $_2$ SO $_4$ at 170°C.
Analyze the transformation: The ethanol loses one H atom and one OH group. • C $_2$ H $_5$ OH $\rightarrow$ C $_2$ H $_4$ + H $_2$ O
Conclude the process: Since water is removed from the molecule to form a new product, the process is defined as dehydration.
Correct Answer
The correct option is C.
Exam Tip
Remember the "Temperature Rule" for ethanol and H $_2$ SO $_4$ :
At 170°C, you get ethene (dehydration/elimination).
At 140°C, you get ethoxyethane (diethyl ether) through a condensation reaction. Always check the temperature in the question—it is the key to distinguishing between these two common JAMB chemistry reactions!
AI can make mistakes. Report anything that looks wrong.
131.
The element which can combine with oxygen to form an acid anhydride of the form XO $_2$ is
1. A.phosphorus
2. B.Chlorine
3. C.fluorine
4. D.sulphur
Show answer
Answer: D. sulphur
AI explanation
Analysis
The question asks us to identify which of the given elements forms an acid anhydride with the general formula $XO_2$ . An acid anhydride is an oxide that reacts with water to form an acid. We need to check which of the options forms a stable dioxide ( $XO_2$ ) that acts as an acid anhydride.
Concept Explanation
Acid Anhydride: These are typically non-metal oxides. When they dissolve in water, they produce an acid.
The Formula $XO_2$ : We are looking for an element $X$ that forms a stable oxide where the ratio of oxygen to the element is 2:1.
Evaluating the options: • Phosphorus (P): Commonly forms $P_4O_{10}$ or $P_4O_6$ . It does not typically exist as a simple $PO_2$ molecule. • Chlorine (Cl): Forms oxides like $Cl_2O$ , $ClO_2$ , and $Cl_2O_7$ . While $ClO_2$ exists, it is a radical and not the most common representative of acid anhydrides in this context. • Fluorine (F): Fluorine is highly electronegative and does not form stable acid anhydrides with oxygen; it forms oxygen fluorides (like $OF_2$ ) where oxygen is the more electronegative atom. • Sulphur (S): Sulphur reacts with oxygen to form Sulphur(IV) oxide ( $SO_2$ ). $SO_2$ is a classic acid anhydride because it reacts with water to form sulphurous acid ( $H_2SO_3$ ): $ $SO_2(g) + H_2O(l) \rightarrow H_2SO_3(aq)$ $
Step-by-Step Solution
Identify the oxide: We are looking for an oxide of the form $XO_2$ .
Test Sulphur: Sulphur burns in oxygen to produce $SO_2$ .
Verify the property: $SO_2$ is a non-metal oxide. Non-metal oxides are acidic in nature.
Check the reaction with water: $SO_2 + H_2O \rightarrow H_2SO_3$ . Since it produces an acid, it is an acid anhydride.
Compare with others: While $ClO_2$ exists, $SO_2$ is the standard textbook example for an acid anhydride of the form $XO_2$ in Nigerian secondary school chemistry curricula.
Conclusion
Sulphur is the element that forms the stable acid anhydride $SO_2$ .
Exam Tip
Remember the "Non-metal Oxide Rule": Most non-metal oxides are acidic (acid anhydrides), while most metal oxides are basic. When you see a question about acid anhydrides, look for the non-metal that forms a stable oxide with oxygen!
AI can make mistakes. Report anything that looks wrong.
132.
The Van der waals forces of attraction operates between
1. A.atoms
2. B.cations
3. C.molecules
4. D.anions
Show answer
Answer: C. molecules
AI explanation
Analysis
The question asks for the specific type of particles between which Van der Waals forces of attraction operate. To answer this, we must understand the nature of intermolecular forces versus intramolecular forces.
Concept Explanation
Van der Waals forces are weak electrostatic attractions that occur between molecules. They are significantly weaker than ionic or covalent bonds (which hold atoms together within a molecule).
Atoms: Held together by covalent or metallic bonds.
Cations and Anions: Held together by strong electrostatic forces known as ionic bonds.
Molecules: These are neutral particles. Because they lack a permanent charge, they rely on weak, temporary fluctuations in electron distribution (London dispersion forces) or permanent dipole-dipole interactions to attract one another. These collective weak attractions are classified as Van der Waals forces.
Step-by-Step Solution
Identify the nature of the force: Van der Waals forces are intermolecular forces, meaning they act between molecules, not within them.
Evaluate the options: • A (Atoms): Atoms are usually held by covalent bonds (e.g., in diamond) or metallic bonds. • B (Cations) & D (Anions): These are charged ions. The force between them is an ionic bond, which is much stronger than Van der Waals forces. • C (Molecules): Van der Waals forces are specifically defined as the forces of attraction between neutral molecules (such as in noble gases or non-polar covalent compounds like $CO_2$ or $CH_4$ ).
Conclusion: Since Van der Waals forces are responsible for the physical properties (like boiling and melting points) of molecular substances, they operate between molecules.
Correct Answer
The correct option is C.
Exam Tip
Remember the hierarchy of bond strength: Ionic/Covalent (Strong) > Hydrogen Bonding (Moderate) > Van der Waals (Weak). If you see a question asking about forces between "molecules," always look for Van der Waals or Hydrogen bonding as your primary candidates!
AI can make mistakes. Report anything that looks wrong.
133.
If the solubility of KNO $_3$ at 30 $^0$ C is 3.10 mol/dm $^3$ a solution containing 303g/dm $^3$ KNO $_3$ is likely to be
1. A.saturated
2. B.unsaturated
3. C.supersaturated
4. D.at saturation point
Show answer
Answer: B. unsaturated
AI explanation
To determine the state of the solution, we need to compare the concentration of the given solution with the solubility limit at the specified temperature.
1. Analyze the question
Given Solubility: 3.10 mol/dm³ at 30°C.
Given Concentration: 303 g/dm³.
Molar Mass of KNO₃: K = 39, N = 14, O = 16. • Molar mass = 39 + 14 + (16 × 3) = 39 + 14 + 48 = 101 g/mol.
2. Explain the concept
Solubility: The maximum amount of solute that can dissolve in a given volume of solvent at a specific temperature.
Conversion: To compare the two values, we must convert the concentration from g/dm³ to mol/dm³ using the formula: $ $\text{Concentration (mol/dm³)} = \frac{\text{Concentration (g/dm³)}}{\text{Molar Mass (g/mol)}}$ $
Comparison: • If the calculated concentration < solubility, the solution is unsaturated. • If the calculated concentration = solubility, the solution is saturated. • If the calculated concentration > solubility, the solution is supersaturated.
3. Show the solution
Step 1: Convert the given concentration (303 g/dm³) to mol/dm³. $ $\text{Concentration} = \frac{303 \text{ g/dm}^3}{101 \text{ g/mol}}$ $ $ $\text{Concentration} = 3.00 \text{ mol/dm}^3$ $
Step 2: Compare the values. • Solubility limit = 3.10 mol/dm³ • Actual concentration = 3.00 mol/dm³ • Since 3.00 mol/dm³ < 3.10 mol/dm³, the solution has not yet reached its maximum capacity to hold the solute.
4. Identify the answer
Because the concentration of the solution (3.00 mol/dm³) is less than the maximum solubility (3.10 mol/dm³), the solution is unsaturated.
*
5. Exam Tip
When dealing with solubility questions, always check your units first! If the solubility is in mol/dm³ and the concentration is in g/dm³, you must convert them to the same unit before comparing. Remember: Molar Mass = Mass / Moles.
AI can make mistakes. Report anything that looks wrong.
134.
A liquid hydrocarbon obtained from fractional distillation of coal tar that is used in the pharmaceutical industry is
1. A.xylene
2. B.benzene
3. C.hexane
4. D.Toluene
Show answer
Answer: B. benzene
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app
135.
What accounts for the low melting and boiling points of covalent molecules?
1. A.They have weak intermolecular forces.
2. B.They are three-dimensional structures.
3. C.They have definite shapes.
4. D.They possess shared electron pairs
Show answer
Answer: A. They have weak intermolecular forces.
AI explanation
Analysis
The question asks for the fundamental reason why covalent molecules (such as water, carbon dioxide, or methane) typically exhibit low melting and boiling points compared to ionic or metallic substances.
Concept Explanation
To understand this, we must distinguish between two types of forces:
Intramolecular forces: These are the strong covalent bonds within the molecule (the sharing of electron pairs). These bonds are very strong and require a lot of energy to break.
Intermolecular forces: These are the weak forces of attraction between separate molecules (such as Van der Waals forces or dipole-dipole interactions).
When a substance melts or boils, we are not breaking the strong covalent bonds inside the molecule; rather, we are providing enough energy to overcome the weak intermolecular forces holding the molecules together in a solid or liquid state. Because these forces are weak, it takes very little heat energy to separate the molecules, resulting in low melting and boiling points.
Step-by-Step Solution
Step 1: Evaluate Option B and C. Having a three-dimensional structure or a definite shape describes the geometry of a molecule, but it does not dictate the energy required to change its state.
Step 2: Evaluate Option D. Shared electron pairs are what form the covalent bond itself. As noted, these bonds are very strong. If we had to break these bonds to melt a substance, covalent molecules would have extremely high melting points (like diamond or silica).
Step 3: Evaluate Option A. Since the molecules are held together by weak intermolecular forces, the energy required to pull them apart is minimal. This directly explains the low melting and boiling points.
Conclusion
Exam Tip: Always remember the "Inter vs. Intra" rule. Intramolecular bonds (covalent/ionic) are strong and hold the structure together; Intermolecular forces (Van der Waals/Hydrogen bonds) are weak and determine physical properties like boiling point, melting point, and volatility.
AI can make mistakes. Report anything that looks wrong.
136.
For chemical reaction to be spontaneous, ∆G must be
1. A.positive
2. B.negative
3. C.zero
4. D.equal to the enthalpy change
Show answer
Answer: B. negative
AI explanation
1. Analyze the question
The question asks for the condition of the Gibbs Free Energy change ( $\Delta G$ ) for a chemical reaction to occur spontaneously. In thermodynamics, spontaneity refers to whether a reaction will proceed on its own without continuous external input of energy.
2. Explain the concept
Gibbs Free Energy ( $\Delta G$ ) is the energy associated with a chemical reaction that can be used to do work. It is defined by the equation:
$\Delta G = \Delta H - T\Delta S$
Where:
$\Delta H$ is the change in enthalpy (heat content).
$T$ is the absolute temperature in Kelvin.
$\Delta S$ is the change in entropy (disorder).
The criteria for spontaneity are:
If $\Delta G < 0$ (negative): The reaction is spontaneous (it happens naturally).
If $\Delta G > 0$ (positive): The reaction is non-spontaneous (it requires energy input to occur).
If $\Delta G = 0$ : The reaction is at equilibrium.
3. Show the solution
Since the question specifically asks for the condition under which a reaction is spontaneous, we look for the value that indicates the system is moving toward a lower energy state, which is the hallmark of a natural, spontaneous process.
According to the Second Law of Thermodynamics, for any spontaneous process, the total entropy of the universe must increase, which mathematically translates to $\Delta G$ being less than zero. Therefore, $\Delta G$ must be negative.
4. Identify the answer
Comparing our explanation to the given options: A. positive (Non-spontaneous) B. negative (Spontaneous) C. zero (Equilibrium) D. equal to the enthalpy change (Only true if $T\Delta S = 0$ )
The correct option is B.
5. Tip
Think of $\Delta G$ like a ball rolling down a hill. A spontaneous reaction is like the ball rolling down naturally—it releases energy, so the change is negative. A non-spontaneous reaction is like trying to push the ball back up the hill—you have to put energy in, so the change is positive.
AI can make mistakes. Report anything that looks wrong.
137.
In the treatment of water for municipal supply, chlorine is used to
1. A.prevent tooth decay
2. B.prevent goitre
3. C.kill germs
4. D.remove colour or odour
Show answer
Answer: C. kill germs
Get a step-by-step AI explanation in the app Get a step-by-step AI explanation in the app

2024 JAMB Chemistry Past Questions — Part 2

Questions 70–137

1. Analyze the Question

2. Explain the Concept

3. Show the Solution

4. Identify the Answer

5. Exam Tip

1. Analyze the Question

2. Explain the Concept

3. Show the Solution

4. Identify the Answer

5. Exam Tip

1. Analyze the question

2. Explain the concept

3. Show the solution

4. Identify the answer

5. Exam Tip

Analysis

Concept Explanation

Step-by-Step Solution

Correct Option

Exam Tip

Analysis

Concept Explanation

Step-by-Step Solution

Conclusion

Exam Tip

Analysis

Concept Explanation

Step-by-Step Solution

Exam Tip

Analysis

Concept Explanation

Step-by-Step Solution

Conclusion

Exam Tip

Analysis of the Question

Concept Explanation

Step-by-Step Solution

Conclusion

Analysis of the Question

Concept Explanation

Step-by-Step Solution

Exam Tip

1. Analyze the Question

2. Explain the Concept

3. Show the Solution

4. Identify the Answer

5. Exam Tip

Step 1: Find the Empirical Formula

Step 2: Find the Molecular Formula

Conclusion

1. Analyze the structure

2. Identify the longest carbon chain

3. Number the chain

4. Assemble the name

Conclusion

Analysis

Concept Explanation

Step-by-Step Solution

Conclusion

1. Analyze the question

2. Explain the concept

3. Show the solution

4. Identify the answer

5. Tip

1. Analyze the Question

2. Explain the Concept

3. Show the Solution

4. Identify the Answer

5. Exam Tip

Analysis

Concept Explanation

Step-by-Step Solution

Exam Tip

1. Analyze the question

2. Explain the concept

3. Show the solution

4. Identify the answer

5. Exam Tip