2016 JAMB Chemistry Past Questions

Questions

1. 1.

   The drying agent suitable for drying ammonia is

   1. A.Calcium Chloride
   2. B.Calcium Oxide
   3. C.Phosphorus(V) Oxide
   4. D.Concentrated H2SO4

   Show answer

   Answer: B. Calcium Oxide

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2. 2.

   Calculate the volume in cm3 of oxygen evolved at s.t.p when a current of 5A is passed through acidified water for 193s? [F = 96500 C mol1. Molar volume of a gas at s.t.p = 22.4dm3]

   1. A.0.056dm3
   2. B.0.224dm3
   3. C.224.000dm3
   4. D.56.000dm3

   Show answer

   Answer: D. 56.000dm3

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3. 3.

   What volume of 0.5M H2SO4 will exactly neutralize 20cm3 of 0.1M NaOH Solution?

   1. A.2.0cm 3
   2. B.5.0cm 3
   3. C.6.8cm 3
   4. D.8.3cm 3

   Show answer

   Answer: A. 2.0cm 3

   AI explanation

   Analysis

   To solve this problem, we need to use the principle of titration (volumetric analysis). We are given the molarity and volume of a base (NaOH) and the molarity of an acid ($H_2SO_4$). We need to find the volume of the acid required to neutralize the base.

   Concept

   The reaction between sulfuric acid ($H_2SO_4$) and sodium hydroxide ($NaOH$) is a neutralization reaction:

   $H_2SO_4 + 2NaOH \rightarrow Na_2SO_4 + 2H_2O$

   From the balanced equation, the mole ratio is:

   • $n_a$ (moles of acid) = 1
   • $n_b$ (moles of base) = 2

   We use the titration formula:

   $\frac{C_a V_a}{C_b V_b} = \frac{n_a}{n_b}$

   Where:

   • $C_a$ = Concentration of acid (0.5 M)
   • $V_a$ = Volume of acid (?)
   • $C_b$ = Concentration of base (0.1 M)
   • $V_b$ = Volume of base (20 $cm^3$)

   Solution

   1. Plug the values into the formula: $$\frac{0.5 \times V_a}{0.1 \times 20} = \frac{1}{2}$$

   2. Simplify the denominator: $$\frac{0.5 \times V_a}{2} = \frac{1}{2}$$

   3. Cross-multiply or solve for $V_a$: $$2 \times (0.5 \times V_a) = 2 \times 1$$ $$1.0 \times V_a = 2$$ $$V_a = 2.0 \, cm^3$$

   Conclusion

   The volume of 0.5M $H_2SO_4$ required to neutralize the base is 2.0 $cm^3$.

   Exam Tip

   Always remember to balance your chemical equation first! Many students forget the mole ratio ($n_a/n_b$) and assume it is always 1:1. In this case, because $H_2SO_4$ is diprotic (has two $H^+$ ions), the ratio is 1:2. If you had used a 1:1 ratio, you would have gotten 4.0 $cm^3$, which is a common distractor in JAMB questions.

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4. 4.

   The products formed when primary Alkanols are oxidized using acidified potassium tetraoxomanganate (VII) are what?

   1. A.CH3CH2CHO and H2O
   2. B.CH3CHO and CO2
   3. C.CH3CH2COOH and H2
   4. D.CH3COOH and CO2

   Show answer

   Answer: A. CH3CH2CHO and H2O

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5. 5.

   In the extraction of iron, the waste gas from the furnace is a mixture of

   1. A.PH3 CO and CO2
   2. B.CO and C
   3. C.N2 , CO and CO2
   4. D.PH3 and CO

   Show answer

   Answer: C. N2 , CO and CO2

   AI explanation

   Analysis

   This question focuses on the industrial extraction of iron using a blast furnace. We need to identify the gaseous by-products that exit the furnace after the reduction of iron ore (usually hematite, $Fe_2O_3$).

   Concept Explanation

   In a blast furnace, several chemical reactions occur as iron ore, coke (carbon), and limestone are heated:

   1. Combustion: Coke burns in the blast of hot air to produce carbon dioxide ($CO_2$) and heat.
   2. Reduction: As $CO_2$ rises, it reacts with more coke to form carbon monoxide ($CO$), which is the primary reducing agent for the iron ore.
   3. Exhaust: The air blast contains a large amount of nitrogen ($N_2$) because air is approximately 78% nitrogen. Since nitrogen is inert, it does not participate in the chemical reactions and passes through the furnace unchanged.

   Consequently, the waste gases leaving the top of the furnace consist of the nitrogen that entered with the air, the carbon dioxide produced from combustion, and the excess carbon monoxide that did not react with the ore.

   Step-by-Step Solution

   1. Identify the input: The blast furnace uses hot air, which is primarily $N_2$ and $O_2$. The $N_2$ passes through the furnace as an inert gas.
   2. Identify the chemical reactions: • $C + O_2 \rightarrow CO_2$ • $CO_2 + C \rightarrow 2CO$
   3. Determine the output: The gases exiting the furnace include the unreacted nitrogen ($N_2$), the carbon dioxide ($CO_2$) produced, and the carbon monoxide ($CO$) that was used as a reducing agent but remained in excess.
   4. Evaluate the options: • Option A and D include $PH_3$ (phosphine), which is not a product of iron extraction. • Option B mentions $C$ (carbon), which is a solid, not a gas. • Option C correctly lists the three main gaseous components: $N_2$, $CO$, and $CO_2$.

   Conclusion

   The mixture of waste gases from the blast furnace is composed of nitrogen, carbon monoxide, and carbon dioxide.

   Exam Tip: Always remember that in any industrial process involving air, nitrogen is almost always present in the waste stream because it is chemically unreactive under these conditions. This simple logic helps eliminate many distractors in chemistry exams!

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6. 6.

   In a neutralization reaction involving HCI and NaOH using litmus as indicator, the colour at the end point is

   1. A.Blue
   2. B.Red
   3. C.Orange
   4. D.Purple

   Show answer

   Answer: D. Purple

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7. 7.

   n monosaccharide $\underset{Q}{\stackrel{P}{\rightleftharpoons}}$ polysaccharide -n water. In the process above, P and Q respectively represent

   1. A.Condensation and hydrolysis
   2. B.Fermentation and condensation
   3. C.Polymerization and hydrolysis
   4. D.Polymerization and condensation

   Show answer

   Answer: A. Condensation and hydrolysis

   AI explanation

   Analysis

   The question asks us to identify the chemical processes represented by P and Q in the conversion between monosaccharides and polysaccharides.

   Concept Explanation

   • Monosaccharides are simple sugars (like glucose).
   • Polysaccharides are complex carbohydrates (like starch or cellulose) made of many monosaccharide units linked together.
   • Condensation Reaction: This is a process where two or more molecules combine to form a larger molecule, usually with the loss of a small molecule like water ($H_2O$). When many monosaccharides join to form a polysaccharide, water is removed.
   • Hydrolysis: This is the reverse process. It involves the breaking down of a complex molecule (like a polysaccharide) into simpler units (monosaccharides) by the addition of water.

   Step-by-Step Solution

   1. Analyze the forward reaction (P): The equation shows $n$ monosaccharides becoming a polysaccharide and losing $n$ water molecules. This is the definition of condensation (specifically, dehydration synthesis). Therefore, P = Condensation.
   2. Analyze the reverse reaction (Q): The equation shows the polysaccharide reacting with water to break back down into $n$ monosaccharides. This is the definition of hydrolysis (literally "splitting with water"). Therefore, Q = Hydrolysis.
   3. Match with the options: We are looking for the pair (P, Q) which corresponds to (Condensation, Hydrolysis).

   Conclusion

   Comparing our findings to the given options:

   • Option A: Condensation and hydrolysis (Matches our derivation).

   Exam Tip

   Think of "Condensation" as "condensing" or squeezing things together to form a bigger structure (releasing water), and "Hydrolysis" as "hydro" (water) + "lysis" (breaking/splitting). Whenever you see water being added to break a bond, it is always hydrolysis!

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8. 8.

   Which of the following is not an alkali?

   1. A.Ca(OH)2
   2. B.NH3
   3. C.NaOH
   4. D.Al(OH)3

   Show answer

   Answer: D. Al(OH)3

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9. 9.

   In an electrochemical cell, polarization is caused by

   1. A.Oxygen
   2. B.Hydrogen
   3. C.Tetraoxosulphate(IV) acid
   4. D.Chlorine

   Show answer

   Answer: B. Hydrogen

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10. 10.

    The gas that is used for the treatment of cancer is

    1. A.Neon
    2. B.Radon
    3. C.Xenon
    4. D.Argon

    Show answer

    Answer: B. Radon

    AI explanation

    Analysis

    The question asks for the specific noble gas that is utilized in medical applications, specifically for the treatment of cancer.

    Concept Explanation

    The noble gases (Group 18 elements) are generally inert, meaning they do not react easily. However, some of them have unique properties that make them useful in specialized fields:

    • Neon: Primarily used in advertising signs and high-voltage indicators.
    • Radon: This is a radioactive noble gas. Because it emits alpha particles, it can be used in radiotherapy to destroy cancerous cells. It is often used in the form of "seeds" implanted directly into or near a tumor to deliver localized radiation.
    • Xenon: Used in specialized light sources, such as camera flashes and some high-intensity lamps.
    • Argon: Used in light bulbs (to prevent the filament from burning) and in welding to provide an inert atmosphere.

    Step-by-Step Solution

    1. Identify the property required: The treatment of cancer (radiotherapy) requires a substance that is radioactive and can emit ionizing radiation to damage the DNA of cancer cells.
    2. Evaluate the options: • Neon, Xenon, and Argon are stable noble gases and are not radioactive. • Radon ($^{222}\text{Rn}$) is the only radioactive noble gas among the choices.
    3. Conclusion: Because Radon is radioactive, it is the only gas listed that is suitable for the medical treatment of cancer through radiotherapy.

    Exam Tip

    When dealing with noble gases in exams, remember their common uses:

    • Helium: Balloons and deep-sea diving (mixed with oxygen).
    • Neon: Signs/Lights.
    • Argon: Inert atmosphere for welding/light bulbs.
    • Radon: Radiotherapy (Cancer treatment).

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11. 11.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

12. 12.

    Which of the following statements is true about 2-methylpropane and butane

    1. A.They have different number of carbon atoms
    2. B.They are members of same homologous series
    3. C.They have the same boiling points
    4. D.They have different chemical properties

    Show answer

    Answer: B. They are members of same homologous series

    AI explanation

    Analysis

    To solve this, we need to look at the molecular structure and classification of the two compounds: 2-methylpropane and butane.

    Concept Explanation

    1. Molecular Formula: • Butane: This is a straight-chain alkane with 4 carbon atoms. Its formula is $C_4H_{10}$. • 2-methylpropane: This is a branched-chain alkane (isobutane). It also has 4 carbon atoms ($3$ in the main chain + $1$ in the methyl group). Its formula is also $C_4H_{10}$.
    2. Homologous Series: A homologous series is a group of organic compounds with the same general formula and similar chemical properties. Both butane and 2-methylpropane are alkanes (general formula $C_nH_{2n+2}$).
    3. Isomerism: Since they have the same molecular formula but different structural arrangements, they are structural isomers.

    Step-by-Step Solution

    • Option A: Both compounds have 4 carbon atoms. Therefore, they do not have a different number of carbon atoms. This statement is false.
    • Option B: Both are alkanes. Since they belong to the same family of hydrocarbons, they are members of the same homologous series. This statement is true.
    • Option C: Boiling points depend on surface area and intermolecular forces. Straight-chain alkanes (butane) have a larger surface area than branched-chain alkanes (2-methylpropane), leading to stronger Van der Waals forces. Thus, they have different boiling points. This statement is false.
    • Option D: Isomers in the same homologous series generally exhibit very similar chemical properties because they share the same functional groups. This statement is false.

    Conclusion

    Exam Tip: Whenever you see two compounds that are isomers of each other, always remember that they will share the same molecular formula and belong to the same homologous series, but they will differ in their physical properties (like boiling point) due to their different shapes!

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13. 13.

    The radioisotope used in industrial radiography for the rapid checking of faults in welds and casting is

    1. A.Phosphorus-32
    2. B.Cobalt-60
    3. C.Carbon-14
    4. D.Iodine-131

    Show answer

    Answer: B. Cobalt-60

    AI explanation

    1. Analyze the question

    The question asks for the specific radioisotope used in industrial applications, specifically for non-destructive testing (NDT) like checking for structural faults in welds and metal castings.

    2. Explain the concept

    Radioisotopes are unstable isotopes of elements that emit radiation. In industrial radiography, we look for isotopes that emit gamma rays. Gamma rays have high penetrating power, allowing them to pass through thick metal objects to reveal internal cracks, voids, or defects on a photographic film (similar to an X-ray).

    • Phosphorus-32: Primarily used in medicine and agriculture as a tracer to study plant metabolism and in treating certain blood disorders.
    • Cobalt-60: A strong gamma-ray emitter. Because of its high energy and long half-life, it is the standard choice for industrial radiography to inspect heavy-duty welds and castings.
    • Carbon-14: Used primarily for radiocarbon dating of organic materials (archaeology).
    • Iodine-131: Used extensively in medicine for diagnosing and treating thyroid gland conditions.

    3. Show the solution

    • Step 1: Identify the purpose of the radioisotope. We need a source of high-energy gamma radiation capable of penetrating dense materials like steel welds.
    • Step 2: Evaluate the options. Phosphorus-32 and Carbon-14 are beta emitters, which lack the penetrating power required for thick metal inspection. Iodine-131 is primarily used for biological/medical applications.
    • Step 3: Confirm the application of Cobalt-60. Cobalt-60 produces high-energy gamma photons that can easily penetrate steel castings, making it the ideal choice for industrial radiography.

    4. Identify the answer

    The correct radioisotope used for checking faults in welds and castings is Cobalt-60. This matches option B.

    5. Exam Tip

    To remember this for your JAMB exam, associate the "C" in Cobalt with Casting and Checking welds. Also, remember that Cobalt-60 is the "heavy lifter" of industrial radiography because of its intense gamma radiation.

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14. 14.

    The metal whose ore can be concentrated by passing it through a magnetic separator is

    1. A.Zn
    2. B.Sn
    3. C.Cu
    4. D.Ca

    Show answer

    Answer: B. Sn

    AI explanation

    1. Analyze the Question

    The question asks for a specific metal whose ore is concentrated using a magnetic separator. This means the ore of the metal must possess magnetic properties, allowing it to be separated from non-magnetic impurities (gangue) when passed over a magnetic belt.

    2. Explain the Concept

    In metallurgy, magnetic separation is a physical method used to concentrate ores where either the ore itself or the impurities are magnetic.

    • Tin (Sn): The primary ore of tin is Cassiterite ($SnO_2$). Cassiterite is often found associated with an impurity called Wolframite ($FeWO_4$ and $MnWO_4$).
    • The Principle: Wolframite is magnetic, while Cassiterite is non-magnetic. By passing the crushed ore over a magnetic separator, the magnetic impurities (Wolframite) are pulled away by the magnet, leaving behind the concentrated Tin ore.
    • Other options: Zinc (Zn), Copper (Cu), and Calcium (Ca) ores are typically concentrated using other methods like froth flotation (for sulfides) or chemical leaching, as they do not rely on magnetic properties for primary concentration.

    3. Show the Solution

    • Step 1: Identify the ore of each metal. • Zn: Zinc blende ($ZnS$) • Sn: Cassiterite ($SnO_2$) • Cu: Copper pyrites ($CuFeS_2$) • Ca: Limestone ($CaCO_3$)
    • Step 2: Evaluate the concentration method. • Cassiterite ($SnO_2$) is the classic example in chemistry textbooks for magnetic separation because it is separated from the magnetic impurity Wolframite.
    • Step 3: Conclusion. Since Cassiterite is the ore that requires magnetic separation to remove magnetic impurities, Tin (Sn) is the correct metal.

    4. Identify the Answer

    The correct option is B.

    5. Exam Tip

    When you see "Magnetic Separator" in a JAMB Chemistry question, immediately look for Tin (Sn) or Cassiterite. If you see "Froth Flotation," look for Sulfide ores (like Copper or Zinc). Remembering these associations will save you time during the exam!

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15. 15.

    Cast iron is used in making

    1. A.Chains and agricultural implements
    2. B.Iron sheets and retort stand
    3. C.Nails and iron rods
    4. D.Stoves and cookers

    Show answer

    Answer: D. Stoves and cookers

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16. 16.

    Which of the following properties is not peculiar to matter?

    1. A.Kinetic energy of particles increases from solid to gas
    2. B.Random motion of particles increases from gas to solid
    3. C.Orderliness of particles increases from gas to liquid
    4. D.Random motion of particles increases from liquid to gas

    Show answer

    Answer: B. Random motion of particles increases from gas to solid

    AI explanation

    To solve this question, we need to understand the Kinetic Molecular Theory of Matter, which describes how particles behave in the three states of matter: solid, liquid, and gas.

    1. Analyze the Question

    The question asks us to identify the statement that is not true (not peculiar) regarding the properties of matter as we transition between states.

    2. Explain the Concepts

    • Kinetic Energy: This is the energy of motion. As you move from solid to liquid to gas, the particles gain more energy and move faster. Therefore, kinetic energy increases from solid to gas.
    • Random Motion: This refers to how freely particles move. Gas particles move randomly and rapidly, while solid particles are fixed in a lattice structure. Therefore, random motion is highest in gases and lowest in solids.
    • Orderliness: This refers to how organized the particles are. Solids are highly ordered, while gases are completely disordered. Therefore, orderliness decreases from solid to gas (or increases from gas to solid).

    3. Evaluate the Options

    • Option A: "Kinetic energy of particles increases from solid to gas." This is true. As heat is added, particles gain energy and move more vigorously.
    • Option B: "Random motion of particles increases from gas to solid." This is false. Random motion is highest in gases and lowest in solids. Moving from gas to solid actually decreases random motion.
    • Option C: "Orderliness of particles increases from gas to liquid." This is true. As you move from a gas (disordered) to a liquid (more structured), the particles become more ordered.
    • Option D: "Random motion of particles increases from liquid to gas." This is true. Gas particles have more freedom of movement than liquid particles.

    4. Identify the Answer

    Since the question asks for the property that is not peculiar (not true), Option B is the correct choice because random motion decreases, rather than increases, when moving from gas to solid.

    5. Exam Tip

    When dealing with states of matter questions, remember the "G-L-S" rule:

    • Gas: High energy, high randomness, low order.
    • Liquid: Medium energy, medium randomness, medium order.
    • Solid: Low energy, low randomness, high order. If a statement suggests that randomness increases as you move toward a solid, it is almost certainly incorrect!

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17. 17.

    The number of electronic shells contained in an atom with electron configuration 1S$^2$2S$^2$2P$^6$3S$^2$3P$^6$4S$^2$ is

    1. A.3
    2. B.2
    3. C.4
    4. D.5

    Show answer

    Answer: C. 4

    AI explanation

    Analysis of the Question

    The question asks for the number of electronic shells present in an atom based on its given electron configuration: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2$.

    Explanation of the Concept

    In electron configuration, the principal quantum number ($n$) represents the main energy level or "shell" of an atom. These are written as the large numbers preceding the subshells ($s, p, d, f$).

    • The configuration is written in order of increasing energy.
    • The highest number appearing as a coefficient in the configuration indicates the outermost shell (valence shell) that contains electrons.
    • The number of shells is simply the value of the highest principal quantum number found in the configuration.

    Step-by-Step Solution

    1. Examine the configuration: $1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2$.
    2. Identify the coefficients: The coefficients (the numbers before the letters) are 1, 2, 2, 3, 3, and 4.
    3. Determine the highest coefficient: The highest number among these is 4.
    4. Interpret the result: This means the electrons occupy energy levels 1, 2, 3, and 4. Therefore, there are 4 electronic shells in this atom.

    Conclusion

    Since the highest principal quantum number is 4, the atom has 4 electronic shells. This corresponds to option C.

    Exam Tip: Always look at the largest number written before the $s, p, d,$ or $f$ orbitals. Don't be distracted by the exponents (the small numbers at the top), as those represent the number of electrons, not the shell number!

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18. 18.

    An example of an acidic oxide is

    1. A.NO
    2. B.CO
    3. C.SO2
    4. D.CuO

    Show answer

    Answer: C. SO2

    AI explanation

    1. Analyze the question

    The question asks us to identify an acidic oxide from the given list. An acidic oxide is typically a non-metal oxide that reacts with water to form an acid or reacts with a base to form a salt and water.

    2. Explain the concept

    • Acidic Oxides: These are usually oxides of non-metals (e.g., $SO_2$, $CO_2$, $P_4O_{10}$). When they dissolve in water, they produce acidic solutions.
    • Basic Oxides: These are usually oxides of metals (e.g., $Na_2O$, $CaO$, $CuO$). They react with acids to form salt and water.
    • Neutral Oxides: These are non-metal oxides that do not react with either acids or bases (e.g., $CO$, $NO$, $N_2O$).
    • Amphoteric Oxides: These are oxides that show both acidic and basic properties (e.g., $Al_2O_3$, $ZnO$).

    3. Show the solution

    Let's evaluate each option:

    • A. NO (Nitrogen(II) oxide): This is a neutral oxide. It does not react with water to form an acid, nor does it react with bases.
    • B. CO (Carbon(II) oxide): This is also a neutral oxide. It is neither acidic nor basic.
    • C. $SO_2$ (Sulfur(IV) oxide): This is a non-metal oxide. When it reacts with water, it forms sulfurous acid: $SO_2(g) + H_2O(l) \rightarrow H_2SO_3(aq)$ Because it forms an acid in water, it is classified as an acidic oxide.
    • D. CuO (Copper(II) oxide): This is a metal oxide. It reacts with acids to form salt and water, which makes it a basic oxide.

    4. Identify the answer

    Based on the analysis, $SO_2$ is the only acidic oxide in the list.

    5. Tip

    A simple way to remember this for your JAMB exam is the "Non-metal rule": Most non-metal oxides are acidic, while most metal oxides are basic. Just watch out for the "Neutral exceptions" like $CO$, $NO$, and $N_2O$—these three are the most common neutral oxides you will encounter in chemistry exams!

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19. 19.

    Diamond cannot be used

    1. A.In making bicycle chains
    2. B.As abrasives
    3. C.In cutting glass and metals
    4. D.As dies for drawing wires

    Show answer

    Answer: A. In making bicycle chains

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20. 20.

    An example of a solid emulsion is

    1. A.Butter
    2. B.Hair cream
    3. C.Milk
    4. D.Cod-liver oil

    Show answer

    Answer: A. Butter

    AI explanation

    Analysis

    The question asks for an example of a solid emulsion. To answer this, we must understand the classification of colloids based on the physical states of the dispersed phase and the dispersion medium.

    Concept: Colloids

    A colloid is a mixture where one substance of microscopically dispersed insoluble particles is suspended throughout another substance. They are classified by the state of the two components:

    • Dispersed Phase: The substance being distributed (the "solute").
    • Dispersion Medium: The substance in which the particles are distributed (the "solvent").

    An emulsion is specifically a colloid where both the dispersed phase and the dispersion medium are liquids. However, a solid emulsion occurs when a liquid is dispersed within a solid medium.

    Step-by-Step Solution

    1. Analyze the options: • Butter: This is a classic example of a solid emulsion. It consists of tiny droplets of water (liquid) dispersed throughout a solid fat (solid). • Hair cream: This is typically a liquid-in-liquid emulsion (oil-in-water or water-in-oil). • Milk: This is a liquid-in-liquid emulsion (fat droplets dispersed in water). • Cod-liver oil: This is a liquid-in-liquid emulsion (often prepared as an emulsion for medicinal purposes).

    2. Evaluate against the definition: Since a solid emulsion requires a liquid dispersed in a solid, butter fits this definition perfectly because it is water trapped inside a solid fat matrix.

    3. Conclusion:

    Exam Tip

    To remember these easily, use this quick table:

    • Liquid in Liquid = Emulsion (e.g., Milk, Mayonnaise)
    • Liquid in Solid = Solid Emulsion (e.g., Butter, Cheese)
    • Gas in Liquid = Foam (e.g., Whipped cream, Soda foam)
    • Solid in Liquid = Sol (e.g., Paints, Mud)

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21. 21.

    N2O4(aq) $\rightleftharpoons$ 2NO2(g) $\bigtriangleup$H = +ve In the reaction above, an increase in temperature will

    1. A.Increase the reactant production
    2. B.Increase the value of the equilibrium constant
    3. C.Shift the equilibrium to the left
    4. D.Decrease the value of the equilibrium constant

    Show answer

    Answer: B. Increase the value of the equilibrium constant

    AI explanation

    Analysis of the Question

    This question tests your understanding of Le Chatelier’s Principle and how temperature changes affect the equilibrium constant ($K$) of a chemical reaction.

    Concept Explanation

    Le Chatelier’s Principle states that if a dynamic equilibrium is disturbed by changing the conditions (like temperature, pressure, or concentration), the position of equilibrium shifts to counteract the change.

    1. Temperature and Equilibrium Shift: • The reaction is given as $\Delta H = +ve$, which means it is an endothermic reaction (it absorbs heat). • In an endothermic reaction, heat acts like a reactant: $\text{Heat} + \text{N}_2\text{O}_4 \rightleftharpoons 2\text{NO}_2$. • If you increase the temperature, the system tries to absorb the excess heat by shifting the equilibrium to the right (the product side).

    2. Temperature and the Equilibrium Constant ($K$): • The equilibrium constant ($K$) is temperature-dependent. • For an endothermic reaction, an increase in temperature increases the concentration of products relative to reactants. Since $K = \frac{[\text{Products}]}{[\text{Reactants}]}$, an increase in products leads to a larger value for $K$.

    Step-by-Step Solution

    • Step 1: Identify the nature of the reaction. Since $\Delta H$ is positive, the forward reaction is endothermic.
    • Step 2: Apply the temperature change. Increasing the temperature provides more energy to the endothermic forward reaction.
    • Step 3: Determine the shift. The equilibrium shifts to the right (towards the products, $\text{NO}_2$).
    • Step 4: Determine the effect on $K$. Because the concentration of the products ($\text{NO}_2$) increases and the concentration of the reactant ($\text{N}_2\text{O}_4$) decreases, the ratio $\frac{[\text{NO}_2]^2}{[\text{N}_2\text{O}_4]}$ increases. Thus, the value of the equilibrium constant increases.

    Evaluation of Options

    • A is incorrect because the equilibrium shifts to the right, increasing product production, not reactant production.
    • B is correct because, for endothermic reactions, $K$ increases as temperature increases.
    • C is incorrect because the equilibrium shifts to the right (forward), not the left.
    • D is incorrect because $K$ only decreases with temperature in exothermic reactions ($\Delta H = -ve$).

    Exam Tip

    Remember the "Endo-Up" rule: For Endothermic reactions, increasing temperature makes the equilibrium constant go Up. For Exothermic reactions, increasing temperature makes the equilibrium constant go Down.

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22. 22.

    The condition required for corrosion to take place is the presence of

    1. A.Oxygen and Carbon (IV) oxide
    2. B.Water and Oxygen
    3. C.Water and Carbon (IV) oxide and Oxygen
    4. D.Water and Carbon (IV) oxide

    Show answer

    Answer: B. Water and Oxygen

    AI explanation

    Analysis of the Question

    The question asks for the essential conditions required for the process of corrosion (specifically the rusting of iron) to occur.

    Explanation of the Concept

    Corrosion is the gradual destruction of materials (usually metals) by chemical reaction with their environment. For iron, this process is known as rusting.

    Rusting is an electrochemical process that requires two primary components to proceed:

    1. Oxygen ($O_2$): This acts as the oxidizing agent.
    2. Water ($H_2O$): This acts as the electrolyte, allowing the flow of ions between the anodic and cathodic regions on the surface of the metal.

    While other substances like salts or acids can accelerate the rate of corrosion, they are not strictly required for the process to initiate. In a dry environment (no water) or an anaerobic environment (no oxygen), iron will not rust.

    Step-by-Step Solution

    1. Evaluate the reaction: The chemical equation for the formation of rust (hydrated iron(III) oxide) is: $4Fe(s) + 3O_2(g) + 2xH_2O(l) \rightarrow 2Fe_2O_3 \cdot xH_2O(s)$
    2. Identify the reactants: From the equation above, it is clear that Iron ($Fe$) reacts with Oxygen ($O_2$) and Water ($H_2O$) to form the hydrated oxide (rust).
    3. Evaluate the options: • A: Carbon (IV) oxide is not a requirement for rusting. • B: Both Water and Oxygen are present in the chemical equation as necessary reactants. • C: While these substances might be present in the atmosphere, Carbon (IV) oxide is not a necessary condition for the chemical reaction of rusting. • D: Water is necessary, but Carbon (IV) oxide is not.

    Conclusion

    This aligns with the scientific principle that rusting is essentially the oxidation of iron in the presence of moisture.

    Exam Tip

    Remember the "Rusting Triangle": Iron + Water + Oxygen = Rust. If you remove any one of these three, the iron will not rust. This is why we paint or oil metal surfaces—to create a barrier that keeps water and oxygen away from the metal!

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23. 23.

    The process that requires the use of hardwater in its operation is

    1. A.Tanning
    2. B.Bottling
    3. C.Laundry
    4. D.Dyeing

    Show answer

    Answer: A. Tanning

    AI explanation

    Analysis

    The question asks us to identify an industrial or domestic process that specifically requires the use of hard water. Hard water contains dissolved calcium ($Ca^{2+}$) and magnesium ($Mg^{2+}$) ions.

    Concept Explanation

    • Hard Water: Water that contains high concentrations of dissolved minerals, specifically calcium and magnesium salts.
    • The Processes: • Laundry: Hard water is generally avoided in laundry because the calcium and magnesium ions react with soap to form "scum" (insoluble calcium/magnesium stearate), which wastes soap and makes cleaning difficult. • Bottling: Bottled water companies usually treat water to remove hardness and impurities to ensure a consistent taste and prevent mineral deposits in pipes. • Dyeing: Hard water is often problematic in dyeing because the mineral ions can react with the dye molecules, leading to uneven coloring or "spotting" on fabrics. • Tanning: In the leather industry, the presence of certain minerals (hardness) can be beneficial. Specifically, in the tanning of leather, calcium salts are often used to help in the "liming" process, which helps remove hair and prepare the hides for tanning.

    Step-by-Step Solution

    1. Evaluate Laundry: Hard water reacts with soap to form scum. This is undesirable, so soft water is preferred.
    2. Evaluate Bottling: Bottling plants prioritize water purity and softness to prevent scaling in machinery and ensure quality.
    3. Evaluate Dyeing: Hard water interferes with the chemical bonding of dyes to fibers, leading to poor results.
    4. Evaluate Tanning: The tanning process involves chemical treatments where calcium compounds are intentionally used to modify the hide structure. Therefore, the presence of hardness (calcium ions) is a functional requirement in this specific industrial process.

    Conclusion

    Among the options provided, Tanning is the process that utilizes the properties of hard water (specifically the calcium content) to facilitate the treatment of animal hides.

    Exam Tip: When you see questions about hard water, always remember the "Soap Rule": If a process involves soap (like laundry), hard water is the enemy! If it involves heavy industrial chemical processing (like tanning), hard water might actually be a requirement.

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24. 24.

    The monomer of nylon is

    1. A.Hydroxybenzene
    2. B.Hexanedioic acid
    3. C.Benzene -1,-4-dicarboxylic acid
    4. D.Ethane-1,2-diol

    Show answer

    Answer: B. Hexanedioic acid

    AI explanation

    Analysis

    The question asks for the monomer (or one of the repeating units) used in the synthesis of Nylon. Nylon is a synthetic polymer known as a polyamide.

    Concept Explanation

    Nylon is produced through a process called condensation polymerization. Specifically, the most common form, Nylon-6,6, is formed by the reaction between two distinct monomers:

    1. Hexanedioic acid (also known as Adipic acid)
    2. Hexamethylenediamine (1,6-diaminohexane)

    In a condensation reaction, the carboxylic acid group (-COOH) of the hexanedioic acid reacts with the amine group (-NH₂) of the diamine, releasing a molecule of water for every bond formed.

    Step-by-Step Solution

    1. Evaluate Option A (Hydroxybenzene): This is phenol. It is used in the production of resins like Bakelite, not Nylon.
    2. Evaluate Option B (Hexanedioic acid): This is a six-carbon dicarboxylic acid. It provides the "acid" part of the amide linkage in Nylon-6,6. It is a fundamental building block for this polymer.
    3. Evaluate Option C (Benzene-1,4-dicarboxylic acid): Also known as terephthalic acid, this is used in the production of polyesters like Terylene (Dacron), not Nylon.
    4. Evaluate Option D (Ethane-1,2-diol): This is ethylene glycol, which is also used in the production of polyesters (like Terylene) when reacted with terephthalic acid.

    Since Nylon-6,6 requires a dicarboxylic acid, Hexanedioic acid is the correct monomer listed among the options.

    Conclusion

    Hexanedioic acid is essential for the formation of the amide bonds that characterize the structure of nylon.

    Exam Tip

    When studying polymers, remember this simple rule:

    • Polyamides (Nylon): Formed from a Dicarboxylic acid + a Diamine.
    • Polyesters (Terylene): Formed from a Dicarboxylic acid + a Diol. Always look for the "acid" component in the options when asked about Nylon!

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25. 25.

    The colour of litmus in an alkaline medium is

    1. A.Red
    2. B.Yellow
    3. C.Pink
    4. D.Blue

    Show answer

    Answer: D. Blue

    AI explanation

    1. Analyze the question

    The question asks for the specific color change observed when litmus, a common acid-base indicator, is placed in an alkaline (basic) solution.

    2. Explain the concept

    Indicators are substances that change color depending on the pH of the solution they are in. Litmus is a natural dye extracted from lichens. Its behavior is summarized by the following rule:

    • In Acidic medium: Litmus turns Red.
    • In Neutral medium: Litmus remains Purple.
    • In Alkaline (Basic) medium: Litmus turns Blue.

    An alkaline medium is characterized by a pH greater than 7, which causes the litmus molecules to undergo a structural change that reflects blue light.

    3. Show the solution

    • Step 1: Identify the nature of the medium. The question specifies an "alkaline medium."
    • Step 2: Recall the indicator property of litmus. Litmus is a standard indicator used to distinguish between acids and bases.
    • Step 3: Apply the property. Since the medium is alkaline, the litmus will shift from its neutral purple state to its basic state.
    • Step 4: Conclusion. The color of litmus in a base is blue.

    4. Identify the answer

    Comparing our conclusion to the given options: A. Red (Acidic) B. Yellow (Common color for Methyl Orange in acid) C. Pink (Common color for Phenolphthalein in acid) D. Blue (Alkaline)

    The correct option is D.

    5. Exam Tip

    To remember this easily, use the mnemonic "B-A-B": Base turns litmus Blue. Conversely, remember that Acids turn litmus Red (think of "Acid" and "Red" both having the letter 'd').

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26. 26.

    The curve depicts titration between a strong acid of pH

    1. A.Strong acid and strong base
    2. B.Strong acid and weak base
    3. C.Weak acid and weak base
    4. D.Weak acid and strong base

    Show answer

    Answer: A. Strong acid and strong base

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27. 27.

    Which of the following compounds is used as a gaseous fuel?

    1. A.CH3 -CH2 -CHO2 -COOH
    2. B.CH3 -C = CH
    3. C.CH3 -CH2 -CH2 -CH3
    4. D.CH2 -CH2 -CH3

    Show answer

    Answer: C. CH3 -CH2 -CH2 -CH3

    AI explanation

    Analysis of the Question

    The question asks us to identify which of the given organic compounds is commonly used as a gaseous fuel. In chemistry, gaseous fuels are typically low-molecular-weight hydrocarbons (alkanes or alkenes) that are gases at room temperature and pressure.

    Concept Explanation

    • Physical State of Alkanes: In the homologous series of alkanes, the first four members ($C_1$ to $C_4$) are gases at room temperature. These include methane, ethane, propane, and butane.
    • Fuel Properties: Because these short-chain hydrocarbons have low boiling points and burn cleanly with oxygen to release significant amounts of energy, they are widely used as fuels (e.g., LPG - Liquefied Petroleum Gas).
    • Evaluating the Options: • Option A: This represents a carboxylic acid derivative. These are generally liquids or solids and are not used as gaseous fuels. • Option B: This is Propyne ($CH_3-C \equiv CH$). While it is a gas, it is primarily used in welding and cutting torches rather than as a standard domestic gaseous fuel. • Option C: This is Butane ($CH_3-CH_2-CH_2-CH_3$). Butane is a four-carbon alkane. It is a gas at room temperature and is a primary component of LPG, making it a standard gaseous fuel. • Option D: This structure is chemically incomplete/incorrect as written, but it does not represent a standard stable gaseous fuel molecule.

    Step-by-Step Solution

    1. Identify the chemical formulas: • A: Represents a complex organic acid structure. • B: Propyne ($C_3H_4$). • C: Butane ($C_4H_{10}$). • D: Incorrectly represented structure.
    2. Determine the state: Butane ($C_4H_{10}$) is a gas at room temperature. It is highly flammable and is stored under pressure in cylinders for use as fuel in homes and industries. 3.

    Conclusion

    Butane is the correct answer because it is a gaseous alkane used extensively as a fuel source.

    Exam Tip: Remember the "Gas Rule" for alkanes: $C_1$ to $C_4$ (Methane to Butane) are gases, $C_5$ to $C_{17}$ are liquids, and $C_{18}$ and above are solids. If you see a question about gaseous fuels, always look for the short-chain alkanes!

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28. 28.

    The functional groups present in the compound above are

    1. A.Alkene and halo-group
    2. B.Hydroxyl and chloro-group
    3. C.Alkene and chloro-group
    4. D.Hydroxyl and halo-group

    Show answer

    Answer: C. Alkene and chloro-group

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29. 29.

    Ammonium chloride can be separated from its mixture with common salt by

    1. A.Distillation
    2. B.Evaporation
    3. C.Decantation
    4. D.Sublimation

    Show answer

    Answer: D. Sublimation

    AI explanation

    Analysis

    The question asks for the most effective method to separate a mixture of two solids: Ammonium chloride ($NH_4Cl$) and common salt (Sodium chloride, $NaCl$).

    Concept

    To choose the right separation technique, we must look at the physical properties of the substances involved:

    1. Sodium chloride ($NaCl$): This is a stable ionic salt that remains solid at high temperatures and does not change state until it reaches its very high melting point.
    2. Ammonium chloride ($NH_4Cl$): This is a covalent compound that exhibits the property of sublimation. Sublimation is the process where a solid changes directly into a gas without passing through the liquid state when heated.

    Solution

    • Step 1: Place the mixture in an evaporating dish or a beaker.
    • Step 2: Apply heat to the mixture.
    • Step 3: As the temperature rises, the ammonium chloride will sublime (turn into vapor).
    • Step 4: You can collect the ammonium chloride vapor by placing an inverted funnel or a cold surface over the container, where it will deposit back into a solid state (desublimation).
    • Step 5: The common salt ($NaCl$) will remain behind in the container because it does not sublime.

    Other options like distillation, evaporation, and decantation are not suitable here because they are designed for separating liquids from solids or liquids from liquids, not for separating two solids based on thermal behavior.

    Conclusion

    Since ammonium chloride sublimes upon heating while common salt does not, sublimation is the correct physical method for this separation.

    Exam Tip

    Whenever you see a question involving Ammonium chloride ($NH_4Cl$), Iodine ($I_2$), or Naphthalene (mothballs) in a mixture, immediately think of sublimation. These are the most common substances tested in JAMB that undergo this process!

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30. 30.

    MnO$_4$(aq) + Y + 5Fe$^{2+}$ (aq) $\mapsto$ Mn$^{2+}$ (aq) + 5Fe$^{3+}$ (aq) + 4H$_2$O (l). In the equation above, Y is

    1. A.10H+ (aq)
    2. B.5H+ (aq)
    3. C.8H+ (aq)
    4. D.4H+ (aq)

    Show answer

    Answer: C. 8H+ (aq)

    AI explanation

    To solve this problem, we need to apply the Law of Conservation of Mass, which states that the number of atoms of each element must be the same on both sides of a chemical equation.

    1. Analyze the Equation

    The given equation is: MnO$_4^-$ (aq) + Y + 5Fe$^{2+}$ (aq) $\rightarrow$ Mn$^{2+}$ (aq) + 5Fe$^{3+}$ (aq) + 4H$_2$O (l)

    We need to determine the value of Y by balancing the atoms that are currently unbalanced.

    2. Explain the Concept

    In redox reactions occurring in acidic media, we balance the oxygen atoms by adding water (H$_2$O) to the side deficient in oxygen. Then, we balance the hydrogen atoms by adding hydrogen ions (H$^+$) to the opposite side.

    3. Step-by-Step Solution

    • Step 1: Check the Oxygen atoms. • Left side: There are 4 oxygen atoms in MnO$_4^-$. • Right side: There are 4 oxygen atoms in 4H$_2$O. • Oxygen is balanced.

    • Step 2: Check the Hydrogen atoms. • Right side: There are 4 molecules of H$_2$O, which means $4 \times 2 = 8$ hydrogen atoms. • Left side: To have 8 hydrogen atoms, Y must contain 8H$^+$.

    • Step 3: Verify the Charge (Optional but recommended). • Left side: $(-1) + 8 + 5(+2) = -1 + 8 + 10 = +17$ • Right side: $(+2) + 5(+3) = 2 + 15 = +17$ • Since the charges are balanced, our identification of Y is correct.

    4. Identify the Answer

    Comparing our result to the options provided, Y must be 8H$^+$ (aq). This matches option C.

    5. Exam Tip

    When balancing redox equations in JAMB Chemistry, always remember the "OH-Charge" sequence:

    1. Balance the main element (Mn and Fe).
    2. Balance Oxygen by adding H$_2$O.
    3. Balance Hydrogen by adding H$^+$.
    4. Balance the Charge by adding electrons (e$^-$). If you follow this order, you will rarely make a mistake!

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31. 31.

    CH4(g) + CI2(g) $\to$ CH2CI(s) + HCIg The major factor that influences the rate of the reaction above is

    1. A.Concentration
    2. B.Catalyst
    3. C.Temperature
    4. D.Light

    Show answer

    Answer: D. Light

    AI explanation

    1. Analyze the Question

    The reaction provided is: CH₄(g) + Cl₂(g) → CH₃Cl(g) + HCl(g) (Note: The chemical formula in your prompt contains a slight typo, but this is clearly a free-radical substitution reaction between methane and chlorine).

    The question asks for the "major factor" that influences the rate of this specific reaction.

    2. Explain the Concept

    This reaction is a photochemical reaction. In organic chemistry, the reaction between alkanes (like methane) and halogens (like chlorine) does not occur spontaneously in the dark at room temperature.

    The reaction proceeds via a free-radical mechanism consisting of three stages:

    • Initiation: The chlorine molecule ($Cl_2$) absorbs energy from ultraviolet (UV) light, causing homolytic fission to produce two chlorine radicals ($Cl^\bullet$).
    • Propagation: The radicals react with methane to form methyl radicals and eventually the product.
    • Termination: Radicals combine to end the reaction.

    Without the presence of light (specifically UV light), the chlorine molecule would not split into the reactive radicals needed to start the chain reaction.

    3. Show the Solution

    • Concentration: While concentration affects the rate of many reactions, it is not the initiating factor for this specific reaction.
    • Catalyst: This reaction does not require a traditional catalyst; it requires a specific form of energy.
    • Temperature: While heat can initiate radical reactions, light is the specific, primary requirement for this chlorination process to proceed at a significant rate under standard conditions.
    • Light: The reaction is defined as a photochemical reaction. The energy from the light (photons) is what breaks the $Cl-Cl$ bond to initiate the process.

    4. Identify the Answer

    The major factor that influences the rate of this reaction is Light.

    5. Exam Tip

    Whenever you see a reaction involving an alkane and a halogen (like $Cl_2$ or $Br_2$) in your JAMB or WASSCE exams, look for UV light or hν (the symbol for a photon) in the options. These reactions are almost always photochemical!

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32. 32.

    What is the concentration of a solution containing 2g of NaOH in 100cm3 of solution? [Na=23, O=16, H=1]

    1. A.0.05 mol$dm^{-3}$
    2. B.0.30 mol$dm^{-3}$
    3. C.0.50 mol$dm^{-3}$
    4. D.0.40 mol$dm^{-3}$

    Show answer

    Answer: C. 0.50 mol$dm^{-3}$

    AI explanation

    Analysis

    To find the concentration of the solution, we need to determine the number of moles of the solute (NaOH) and divide it by the volume of the solution in cubic decimeters ($dm^3$).

    Concept

    1. Molar Mass Calculation: First, find the molar mass of NaOH by summing the atomic masses of its constituent elements.
    2. Mole Calculation: Use the formula: $\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}}$.
    3. Volume Conversion: Since the volume is given in $cm^3$, convert it to $dm^3$ by dividing by 1000 ($1000 cm^3 = 1 dm^3$).
    4. Concentration Calculation: Use the formula: $\text{Concentration (mol/dm}^3) = \frac{\text{Moles}}{\text{Volume in dm}^3}$.

    Step-by-Step Solution

    Step 1: Calculate the Molar Mass of NaOH

    • Na = 23, O = 16, H = 1
    • Molar Mass of NaOH = $23 + 16 + 1 = 40 \text{ g/mol}$

    Step 2: Calculate the number of moles of NaOH

    • $\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}}$
    • $\text{Moles} = \frac{2 \text{ g}}{40 \text{ g/mol}} = 0.05 \text{ moles}$

    Step 3: Convert volume from $cm^3$ to $dm^3$

    • $\text{Volume} = \frac{100 cm^3}{1000} = 0.1 dm^3$

    Step 4: Calculate the concentration

    • $\text{Concentration} = \frac{\text{Moles}}{\text{Volume in dm}^3}$
    • $\text{Concentration} = \frac{0.05 \text{ mol}}{0.1 dm^3} = 0.5 \text{ mol/dm}^3$

    Conclusion

    Comparing our result to the given options, the concentration is $0.50 \text{ mol/dm}^3$. This matches option C.

    Exam Tip

    Always watch your units! JAMB examiners love to give volumes in $cm^3$ to see if you remember to convert to $dm^3$ (by dividing by 1000) before calculating molarity. A common mistake is to divide by 100 instead of 1000.

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33. 33.

    The relative atomic mass of a naturally occurring lithium consisting of 90%$\frac{7}{3}$Li and 10%$\frac{6}{3}$Li is

    1. A.6.2
    2. B.6.8
    3. C.7.1
    4. D.6.9

    Show answer

    Answer: D. 6.9

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34. 34.

    Ethanol is soluble in water due to the presence of a

    1. A.Carbonyl group
    2. B.Hydroxyl group
    3. C.Phenyl group
    4. D.Methyl group

    Show answer

    Answer: B. Hydroxyl group

    AI explanation

    1. Analyze the question

    The question asks for the specific functional group responsible for the solubility of ethanol ($C_2H_5OH$) in water.

    2. Explain the concept

    Solubility in water is largely determined by the ability of a molecule to form hydrogen bonds with water molecules.

    • Ethanol consists of an alkyl chain (ethyl group) and a functional group attached to it.
    • The hydroxyl group (-OH) is polar. Because oxygen is highly electronegative, it creates a dipole moment, allowing the hydrogen atom in the -OH group to form hydrogen bonds with the oxygen atoms in water molecules.
    • This interaction between the solute (ethanol) and the solvent (water) is what makes ethanol miscible (soluble) in water in all proportions.

    3. Show the solution

    • Option A (Carbonyl group): This is found in aldehydes and ketones ($C=O$). While polar, it is not the group present in ethanol.
    • Option B (Hydroxyl group): This is the $-OH$ group. It is the defining functional group of alcohols. It allows for hydrogen bonding, which is the primary reason for the solubility of short-chain alcohols like ethanol in water.
    • Option C (Phenyl group): This is a benzene ring ($C_6H_5-$). It is non-polar and hydrophobic, which would actually decrease solubility in water.
    • Option D (Methyl group): This is $-CH_3$. It is non-polar and hydrophobic.

    Since ethanol is an alcohol, it contains the hydroxyl group, which facilitates its dissolution in water.

    4. Identify the answer

    The correct option is B.

    5. Exam Tip

    Remember the "Like Dissolves Like" rule: Polar substances dissolve in polar solvents. Since water is a highly polar solvent, it dissolves substances that can form hydrogen bonds. Whenever you see an alcohol (ending in "-ol"), immediately associate it with the Hydroxyl (-OH) group and its ability to hydrogen bond!

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35. 35.

    An isotope has an atomic number of 15 and a mass number of 31. The number of proton it contains is

    1. A.16
    2. B.15
    3. C.31
    4. D.46

    Show answer

    Answer: B. 15

    AI explanation

    Analysis

    The question asks for the number of protons in an atom given its atomic number and mass number.

    Concept Explanation

    To solve this, you need to understand the basic structure of an atom:

    1. Atomic Number ($Z$): This represents the number of protons in the nucleus of an atom. It is the unique identifier for every element (e.g., Phosphorus has an atomic number of 15).
    2. Mass Number ($A$): This is the sum of the number of protons and neutrons in the nucleus ($A = \text{protons} + \text{neutrons}$).
    3. Neutral Atom: In a neutral atom, the number of protons is equal to the number of electrons.

    Step-by-Step Solution

    • Step 1: Identify the given information. • Atomic number ($Z$) = 15 • Mass number ($A$) = 31
    • Step 2: Apply the definition of atomic number. • By definition, the atomic number is exactly equal to the number of protons. • Therefore, Number of protons = Atomic number = 15.
    • Step 3: (Optional) Calculate neutrons for extra practice. • Neutrons = Mass number - Atomic number • Neutrons = 31 - 15 = 16.

    Since the question specifically asks for the number of protons, we look directly at the atomic number provided.

    Conclusion

    The number of protons is 15. This matches option B.

    Exam Tip

    Always remember the acronym "APE": Atomic number = Protons = Electrons (in a neutral atom). If you ever get confused, just remember that the atomic number is the "identity card" of the element, and it always tells you the proton count!

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36. 36.

    Which of the following statements is correct about the periodic table?

    1. A.Elements in the same group have the same number of electron shells
    2. B.The non-metallic properties of the elements tend to decrease across each period
    3. C.Elements in the same period have the same number of valence electrons
    4. D.The valence electrons of the elements increase progressively across the period

    Show answer

    Answer: D. The valence electrons of the elements increase progressively across the period

    AI explanation

    Analysis of the Question

    This question tests your understanding of the trends and organizational principles of the Periodic Table. To solve this, we need to evaluate how electron configuration determines an element's position (Group and Period) and how properties change as you move across a period.

    Concept Explanation

    1. Groups (Vertical Columns): Elements in the same group have the same number of valence electrons (electrons in the outermost shell). This is why they exhibit similar chemical properties.
    2. Periods (Horizontal Rows): Elements in the same period have the same number of electron shells.
    3. Trends across a Period: As you move from left to right across a period: • The number of valence electrons increases by one for each subsequent element. • The atomic radius generally decreases. • Metallic character decreases, and non-metallic character increases.

    Step-by-Step Evaluation

    • Option A: Incorrect. Elements in the same period have the same number of electron shells, not the same group.
    • Option B: Incorrect. Non-metallic properties actually increase across a period (from left to right, elements go from metals to metalloids to non-metals).
    • Option C: Incorrect. Elements in the same group have the same number of valence electrons, not the same period.
    • Option D: Correct. As you move across a period (e.g., from Lithium to Neon in Period 2), each element adds one proton to the nucleus and one electron to the valence shell. Therefore, the number of valence electrons increases progressively (1, 2, 3, 4, 5, 6, 7, 8).

    Conclusion

    Exam Tip

    Remember the mnemonic: "G-V-P-S"

    • Group = Valence electrons (same)
    • Period = Shells (same)

    This simple trick will help you avoid mixing up the definitions of groups and periods during your JAMB exam!

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37. 37.

    The compound produced when sodium peroxide is heated with excess sodium is

    1. A.Na2CO3
    2. B.Na2O
    3. C.NaNO2
    4. D.NaOH

    Show answer

    Answer: B. Na2O

    AI explanation

    1. Analyze the question

    The question asks for the product formed when sodium peroxide ($\text{Na}_2\text{O}_2$) reacts with excess sodium metal ($\text{Na}$) under heating.

    2. Explain the concept

    In chemistry, sodium peroxide is a strong oxidizing agent. When it reacts with an excess of a reducing agent like sodium metal, the sodium metal reduces the peroxide to a more stable oxide.

    The reaction involves the transfer of electrons from the sodium atoms to the oxygen atoms within the peroxide structure. Because there is an excess of sodium, the reaction proceeds until the sodium peroxide is fully converted into the most stable form of sodium oxide, which is sodium oxide ($\text{Na}_2\text{O}$).

    3. Show the solution

    The chemical equation for this reaction is:

    $\text{Na}_2\text{O}_2 + 2\text{Na} \rightarrow 2\text{Na}_2\text{O}$

    • Reactants: Sodium peroxide ($\text{Na}_2\text{O}_2$) and Sodium ($\text{Na}$).
    • Process: The sodium metal reacts with the oxygen in the peroxide. Since the sodium is in excess, all the peroxide is consumed to form the simple oxide.
    • Product: Sodium oxide ($\text{Na}_2\text{O}$).

    4. Identify the answer

    Comparing our result to the given options: A. $\text{Na}_2\text{CO}_3$ (Sodium trioxocarbonate IV) B. $\text{Na}_2\text{O}$ (Sodium oxide) C. $\text{NaNO}_2$ (Sodium trioxonitrate III) D. $\text{NaOH}$ (Sodium hydroxide)

    The correct option is B.

    5. Tip

    When dealing with Group 1 metals (like Sodium) and oxygen, remember the "excess" rule:

    • If there is excess oxygen, you typically get the peroxide ($\text{Na}_2\text{O}_2$).
    • If there is excess metal, you typically get the simple oxide ($\text{Na}_2\text{O}$).

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38. 38.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

39. 39.

    Alkanols have the general molecular formula

    1. A.CnH2n-2
    2. B.CnH2n+1CHO
    3. C.CnH2n-2OH
    4. D.CnH2n+1OH

    Show answer

    Answer: D. CnH2n+1OH

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40. 40.

    In the laboratory preparation of chlorine from concentrated hydrochloric acid in the presence of potassuim tetraoxomanganate(VII) the produced is dried by passing it through

    1. A.Concentrated tetraoxosulphate (VI) acid
    2. B.Anhydrous calcium chloride
    3. C.Calcium oxide
    4. D.Sodium hydroxide

    Show answer

    Answer: A. Concentrated tetraoxosulphate (VI) acid

    AI explanation

    Analysis of the Question

    The question asks for the drying agent used to remove moisture from chlorine gas ($Cl_2$) produced in the laboratory. Chlorine is an acidic gas, so the drying agent must be one that does not react with it.

    Concept Explanation

    In the laboratory, chlorine is prepared by the reaction of concentrated hydrochloric acid ($HCl$) with potassium tetraoxomanganate(VII) ($KMnO_4$). The gas produced is usually moist. To dry a gas, we pass it through a substance that absorbs water but does not chemically react with the gas being dried.

    • Concentrated tetraoxosulphate(VI) acid ($H_2SO_4$): This is a powerful dehydrating agent. It is acidic and does not react with chlorine gas, making it the standard choice for drying chlorine.
    • Calcium oxide ($CaO$): This is a basic oxide. It would react with chlorine gas to form calcium chloride and calcium hypochlorite.
    • Sodium hydroxide ($NaOH$): This is an alkali. It reacts readily with chlorine gas to form sodium chloride and sodium oxochlorate(I) (bleach).
    • Anhydrous calcium chloride ($CaCl_2$): While often used as a drying agent, it is generally used for neutral or acidic gases, but in the specific context of the laboratory preparation of chlorine, concentrated $H_2SO_4$ is the preferred industrial and laboratory standard for drying.

    Step-by-Step Solution

    1. Identify the gas: The gas is chlorine ($Cl_2$), which is acidic.
    2. Evaluate the options: • D: Sodium hydroxide is a base; it will absorb the chlorine gas (neutralization), so it cannot be used. • C: Calcium oxide is a base; it will react with the chlorine gas. • B: Anhydrous calcium chloride is a drying agent, but concentrated tetraoxosulphate(VI) acid is the specific reagent used in the standard laboratory setup for this preparation to ensure the gas is effectively dried without interference. • A: Concentrated tetraoxosulphate(VI) acid ($H_2SO_4$) is acidic and has a high affinity for water. It effectively removes moisture from the chlorine gas without reacting with it.

    Conclusion

    Concentrated tetraoxosulphate(VI) acid is the standard drying agent for chlorine gas in this preparation.

    Exam Tip

    Always remember the "Acid-Base" rule for drying gases:

    • Acidic gases (like $Cl_2$, $SO_2$, $HCl$) are dried using acidic drying agents (like conc. $H_2SO_4$).
    • Basic gases (like $NH_3$) are dried using basic drying agents (like calcium oxide).
    • Neutral gases (like $O_2$, $N_2$) can be dried using a variety of agents.

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41. 41.

    The principle of column chromatography is based on th ability of the constituents to

    1. A.React with the solvent in the column
    2. B.React with each other in the solvent in the column
    3. C.Dissolve in each other in the column
    4. D.Move at different speeds in the column

    Show answer

    Answer: D. Move at different speeds in the column

    AI explanation

    Analysis

    This question tests your understanding of Separation Techniques, specifically Chromatography, which is a core topic in the Chemistry syllabus for JAMB and WASSCE. You are asked to identify the fundamental principle that allows column chromatography to separate a mixture.

    Concept Explanation

    Column Chromatography is a technique used to separate components of a mixture based on the differences in their adsorption or partition between two phases:

    1. The Stationary Phase: A solid material (usually silica gel or alumina) packed inside a glass column.
    2. The Mobile Phase: A solvent (eluent) that flows through the column.

    As the mixture travels through the column with the solvent, the different components interact with the stationary phase to varying degrees. Some components "stick" (adsorb) more strongly to the stationary phase, while others remain more soluble in the mobile phase. Because of these differences in affinity, the components travel through the column at different rates.

    Step-by-Step Solution

    1. Analyze the movement: As the solvent flows down the column, the components of the mixture are carried along.
    2. Differential rates: Because each component has a different affinity for the stationary phase versus the mobile phase, they do not move at the same speed.
    3. Separation: The component that has the least affinity for the stationary phase moves faster and exits the column first, while the component with the highest affinity moves the slowest.
    4. Conclusion: The entire process relies on the fact that these constituents move at different speeds through the stationary phase, allowing them to be collected separately at different times.

    • Option A & B: Chromatography is generally a physical separation technique; it does not rely on chemical reactions between the constituents or the solvent.
    • Option C: Dissolving in each other is not the mechanism of separation; the components are already dissolved in the mobile phase.
    • Option D: This accurately describes the physical basis of the separation.

    Final Answer

    The correct option is D.

    Exam Tip

    Think of chromatography like a race on a track with obstacles. The "runners" (constituents) have different levels of energy and agility (affinity). Those who are less hindered by the obstacles (stationary phase) finish the race (exit the column) faster than those who get stuck or slowed down by them. This difference in speed is exactly how you separate them!

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42. 42.

    The compound above exhibits

    1. A.Geometric isomerism
    2. B.Positional isomerism
    3. C.Structural isomerism
    4. D.Optical isomerism

    Show answer

    The answer for this question isn't available yet.

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43. 43.

    The diagram represents

    1. A.A spontaneous reaction
    2. B.An exothermic reaction
    3. C.A non-spontaneous
    4. D.An endothermic reaction

    Show answer

    Answer: C. A non-spontaneous

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44. 44.

    A chemical reaction in which the hydration energy is greater than the lattice energy is referred to as

    1. A.A reversible reaction
    2. B.A spontenous reaction
    3. C.An endothermic reaction
    4. D.An exothermic reaction

    Show answer

    Answer: D. An exothermic reaction

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45. 45.

    The ability of carbon to form long chains is referred to as

    1. A.Alkylation
    2. B.Acylation
    3. C.Carbonation
    4. D.Catenation

    Show answer

    Answer: D. Catenation

    AI explanation

    1. Analyze the question

    The question asks for the specific term used to describe the unique chemical property of carbon atoms to bond with other carbon atoms to form long, stable chains, branched structures, or rings.

    2. Explain the concept

    In organic chemistry, carbon is unique because of its electronic configuration ($1s^2 2s^2 2p^2$). It has four valence electrons, allowing it to form four strong covalent bonds. Because the carbon-carbon (C-C) bond is very strong and stable, carbon atoms can link together repeatedly. This phenomenon is fundamental to the existence of the millions of organic compounds found in nature, including plastics, proteins, and DNA.

    • Alkylation is the transfer of an alkyl group from one molecule to another.
    • Acylation is the process of adding an acyl group to a compound.
    • Carbonation is the process of dissolving carbon dioxide in a liquid (like in soft drinks).
    • Catenation is the specific term for the self-linking property of atoms of the same element to form chains.

    3. Show the solution

    • Step 1: Identify the definition of the property described. The ability to form long chains is the definition of catenation.
    • Step 2: Evaluate the options. • A, B, and C describe chemical reactions or processes, not a structural property of an element. • D (Catenation) is the scientific term for the self-linking property of carbon.

    4. Identify the answer

    The correct option is D.

    5. Tip

    Memory Trick: Think of the word "Chain". Catenation starts with "Cat-", which sounds like the beginning of "Chain". Remember: Carbon = Catenation = Chains. This property is why organic chemistry is such a vast field of study!

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46. 46.

    The enzyme used in the hydrolysis of starch to dextrin and maltose is

    1. A.Zymase
    2. B.Sucrase
    3. C.Amylase
    4. D.Lactase

    Show answer

    Answer: C. Amylase

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47. 47.

    The industrial preparation of hydrogen gas from water gas is referred to as

    1. A.Bosch process
    2. B.Contact process
    3. C.Haber process
    4. D.Bayer Process

    Show answer

    Answer: A. Bosch process

    AI explanation

    Analysis

    The question asks for the specific industrial process used to produce hydrogen gas from "water gas" (a mixture of carbon(II) oxide and hydrogen).

    Concept Explanation

    To understand this, we must look at the two-stage production of hydrogen from coal:

    1. Water Gas Production: Steam is passed over red-hot coke to produce water gas: $C(s) + H_2O(g) \rightarrow CO(g) + H_2(g)$
    2. Hydrogen Enrichment (The Bosch Process): The carbon(II) oxide ($CO$) in the water gas is reacted with more steam in the presence of a catalyst (iron(III) oxide) at high temperatures. This converts the $CO$ into $CO_2$, which is then removed, leaving behind a higher concentration of hydrogen gas: $CO(g) + H_2O(g) \rightleftharpoons CO_2(g) + H_2(g)$

    This second stage, where $CO$ is converted to $CO_2$ to increase the yield of hydrogen, is known as the Bosch process.

    Evaluation of Options

    • A. Bosch process: This is the correct industrial method for obtaining hydrogen from water gas.
    • B. Contact process: This is the industrial method for the manufacture of sulphuric acid.
    • C. Haber process: This is the industrial method for the manufacture of ammonia.
    • D. Bayer process: This is the industrial method for the extraction of alumina (aluminium oxide) from bauxite ore.

    Conclusion

    The industrial preparation of hydrogen gas from water gas is the Bosch process.

    Exam Tip

    To avoid confusion in the exam hall, remember these "Industrial Process" pairings:

    • Haber = Ammonia ($NH_3$)
    • Contact = Sulphuric Acid ($H_2SO_4$)
    • Bosch = Hydrogen ($H_2$)
    • Bayer = Aluminium ($Al$)

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48. 48.

    The compounds CH3CH2CHO and CH3COCH3 can be distinguished from each other using

    1. A.Dilute ammonia
    2. B.Benedict's solution
    3. C.Tollen's reagent
    4. D.Sodium hydroxide solution

    Show answer

    Answer: C. Tollen's reagent

    AI explanation

    Analysis

    The question asks us to distinguish between two organic compounds: CH₃CH₂CHO (propanal) and CH₃COCH₃ (propanone).

    • CH₃CH₂CHO is an aldehyde.
    • CH₃COCH₃ is a ketone.

    To distinguish between them, we need a chemical test that reacts with aldehydes but does not react with ketones.

    Concept: Oxidation of Carbonyl Compounds

    • Aldehydes are easily oxidized to carboxylic acids because they possess a hydrogen atom attached to the carbonyl carbon.
    • Ketones are resistant to mild oxidation because they lack that hydrogen atom.

    Common laboratory reagents used to distinguish aldehydes from ketones include Tollen's reagent and Fehling's solution/Benedict's solution.

    Step-by-Step Solution

    1. Analyze the Reagents: • Tollen's reagent (Ammoniacal silver nitrate): When heated with an aldehyde, it is reduced to metallic silver, forming a "silver mirror" on the walls of the test tube. Ketones do not react with Tollen's reagent. • Benedict's solution: When heated with an aliphatic aldehyde, it produces a reddish-brown precipitate of copper(I) oxide. Ketones do not react with Benedict's solution.

    2. Evaluate the Options: • A (Dilute ammonia): Does not react with either to give a distinct visual difference. • B (Benedict's solution): While this can distinguish them, Tollen's reagent is the classic, most definitive textbook reagent for this specific distinction in JAMB chemistry. • C (Tollen's reagent): This is the standard reagent used to identify aldehydes. The formation of a silver mirror confirms the presence of the aldehyde (propanal), while the ketone (propanone) remains unchanged. • D (Sodium hydroxide): Used in condensation reactions, but not as a primary diagnostic test to distinguish these two.

    3. Conclusion: Both B and C are chemically capable of distinguishing them; however, in the context of JAMB and standard chemistry examinations, Tollen's reagent is the primary and most widely cited answer for distinguishing aldehydes from ketones.

    Tip for your Exam

    Remember the mnemonic "Aldehydes are Silver-tongued": Aldehydes react with Tollen's reagent to form a silver mirror. Ketones are "stubborn" and do not react with mild oxidizing agents like Tollen's or Benedict's.

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49. 49.

    The arrangement of particles in crystal lattices can be studied using

    1. A.X-rays
    2. B.$\beta$-rays
    3. C.$\alpha$-rays
    4. D.$\gamma$-rays

    Show answer

    Answer: A. X-rays

    AI explanation

    Analysis

    The question asks for the specific scientific tool or type of radiation used to determine the internal structure and arrangement of atoms within a crystal lattice.

    Concept Explanation

    In chemistry and physics, a crystal lattice is a highly ordered, repeating 3D arrangement of particles (atoms, ions, or molecules). Because these particles are spaced at distances comparable to the wavelength of X-rays (approximately $10^{-10}$ meters), X-rays are uniquely suited for this purpose.

    When a beam of X-rays strikes a crystal, the rays are scattered by the electrons of the atoms in the lattice. This phenomenon is known as X-ray diffraction. By analyzing the pattern of the diffracted rays (the diffraction pattern), scientists can calculate the precise positions of atoms, the bond lengths, and the bond angles within the crystal. This technique is famously known as X-ray crystallography.

    Step-by-Step Solution

    1. Evaluate the options: • $\alpha$-rays (Alpha particles): These are heavy, positively charged particles. They have low penetrating power and are mostly used in nuclear physics experiments (like the Rutherford gold foil experiment), not for mapping crystal lattices. • $\beta$-rays (Beta particles): These are high-energy electrons. They are generally used in medical imaging or industrial thickness gauging, not for structural analysis of crystals. • $\gamma$-rays (Gamma rays): These have very high energy and extremely short wavelengths. While they can penetrate matter, they are generally too energetic for standard diffraction studies of crystal lattices. • X-rays: These have the perfect wavelength range to interact with the atomic spacing in crystals, allowing for constructive interference that creates a measurable diffraction pattern.

    2. Conclusion: X-ray diffraction is the standard laboratory method for determining the arrangement of particles in a crystal lattice.

    Exam Tip

    Whenever you see a question about "crystal structure," "atomic spacing," or "diffraction patterns," immediately think of X-rays. Remember the name Bragg’s Law ($n\lambda = 2d \sin\theta$); it is the fundamental equation used in X-ray crystallography to relate the wavelength of the X-rays to the spacing of the crystal planes.

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50. 50.

    The pollutant that contributes to the depletion of the ozone layer is

    1. A.CFCs
    2. B.NO2
    3. C.SO2
    4. D.CO

    Show answer

    Answer: A. CFCs

    AI explanation

    Analysis

    The question asks for the specific pollutant responsible for the depletion of the ozone layer. To answer this, we need to understand the chemical process occurring in the stratosphere and identify which substances interfere with the ozone ($O_3$) cycle.

    Concept Explanation

    The ozone layer acts as a shield, protecting the Earth from harmful ultraviolet (UV) radiation. The depletion of this layer occurs when certain chemicals reach the stratosphere and react with ozone molecules, breaking them down into oxygen ($O_2$).

    • CFCs (Chlorofluorocarbons): These are synthetic compounds containing chlorine, fluorine, and carbon. When they reach the upper atmosphere, UV radiation breaks them down, releasing chlorine atoms. A single chlorine atom can destroy thousands of ozone molecules through a catalytic chain reaction.
    • NO2 (Nitrogen dioxide): While it contributes to acid rain and photochemical smog, it is not the primary driver of ozone depletion.
    • SO2 (Sulfur dioxide): This is a major contributor to acid rain and air pollution, but it does not deplete the ozone layer.
    • CO (Carbon monoxide): This is a toxic gas produced by incomplete combustion. It binds to hemoglobin in the blood, preventing oxygen transport, but it does not affect the ozone layer.

    Step-by-Step Solution

    1. Identify the mechanism: Ozone depletion is primarily caused by the release of free radicals (like chlorine or bromine) into the stratosphere.
    2. Evaluate the options: • CFCs are stable at ground level but decompose in the stratosphere to release chlorine radicals. • The other gases (NO2, SO2, CO) are primarily tropospheric pollutants that affect air quality and climate, but they do not possess the specific chemical property of catalytic ozone destruction in the stratosphere.
    3. Conclusion: CFCs are the well-documented culprits behind the "ozone hole."

    Exam Tip

    When you see questions about Ozone Depletion, always look for CFCs (Chlorofluorocarbons). When you see questions about Acid Rain, look for SO2 or NO2. Remembering this distinction will save you time in the exam hall!

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