2018 WAEC (WASSCE) Chemistry Past Questions

Questions

1. 1.

   An acidic salt has

   1. A.double anions in its aqueous solution
   2. B.a single cation in its aqueous solution
   3. C.hydrogen ions in its aqueous solution
   4. D.hydrogen atoms in its aqueous solution

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   Answer: C. hydrogen ions in its aqueous solution

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2. 2.

   Stainless steel is an alloy comprising of

   1. A.Fe and C
   2. B.Fe and Ni
   3. C.Fe, C and Ni
   4. D.Fe, C and Al

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   Answer: C. Fe, C and Ni

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3. 3.

   Which of the following properties would not influence electrovalent bond formation?

   1. A.Electronegativity
   2. B.Electron Affinity
   3. C.Ionization potential
   4. D.Catalytic ability

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   Answer: D. Catalytic ability

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4. 4.

   One of the criteria for confirming the purity of benzene is to determine its

   1. A.heat capacity
   2. B.boiling point
   3. C.mass
   4. D.colour

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   Answer: B. boiling point

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5. 5.

   Which of the following electron configurations represents the transition element Chromium $_{24}Cr$?

   1. A.$1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{2} 3d^{4}$
   2. B.$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{6}$
   3. C.$1s^{2}2s^{2}2p^{6}3s^{2}3d^{4} 4s^{1}$
   4. D.$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{5}$

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   Answer: D. $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{5}$

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6. 6.

   Which of the following methods can be used to seperate blood cells from plasma?

   1. A.Centrifugation
   2. B.Filtration
   3. C.Chromatography
   4. D.Distillation

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   Answer: A. Centrifugation

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7. 7.

   The valence electrons of $_{12}Mg$ are in the

   1. A.3s orbital
   2. B.2p$_{x}$
   3. C.2s orbital
   4. D.1s orbital

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   Answer: A. 3s orbital

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8. 8.

   An organic compound has the empirical formula $CH_{2}$. If its molar mass is 42$gmol^{-1}$, what is its molecular formula?  (C = 12.0, H = 1.0)

   1. A.$C_{2}H_{4}$
   2. B.$C_{3}H_{4}$
   3. C.$C_{3}H_{6}$
   4. D.$C_{4}H_{8}$

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   Answer: C. $C_{3}H_{6}$

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9. 9.

   What is the relative molecular mass of a compound which has empirical formula $CH_{2}O$?   [C= 12, H= 1, O= 16]

   1. A.42
   2. B.45
   3. C.126
   4. D.180

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   Answer: D. 180

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10. 10.

    The empirical formula of a compound containing 0.067mol Cu and 0.066mol O is    [Cu = 63.5, O = 16]

    1. A.$Cu_{2}O$
    2. B.$CuO$
    3. C.$CuO_{2}$
    4. D.$CuO_{4}$

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    Answer: B. $CuO$

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11. 11.

    Particles in a solid exibit

    1. A.vibrational motion
    2. B.vibrational and translational motion
    3. C.vibrational and random motion
    4. D.random and translational motion

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    Answer: A. vibrational motion

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12. 12.

    The solubility of $CO_{2}$ in water can be accounted for by

    1. A.Van der Waal's forces
    2. B.Ionic attraction
    3. C.dipole attraction
    4. D.covalent bonding

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    Answer: A. Van der Waal's forces

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13. 13.

    Common Salt (NaCl) is used to preserve foods. Which of the following properties can be used to determine its purity before use?

    1. A.Solubility in water
    2. B.Melting point
    3. C.Relative density
    4. D.Crystalline nature

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    Answer: B. Melting point

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14. 14.

    Which of the following equations represents a redox reaction?

    1. A.$HNO_{{3}{(aq)}} + NaOH_{(aq)} \to NaNO_{{3}{(aq)}} + H_{2}O_{(l)}$
    2. B.$AgNO_{{3}{(aq)}}+KCl_{(aq)} \to AgCl_{(s)}+KNO_{{3}{(aq)}}$
    3. C.$CaCO_{{3}{(s)}} \to CaO_{(s)} + CO_{{2}{(g)}}$
    4. D.$2H_{2}S_{(s)} + SO_{{2}{(g)}} \to 2HO_{2} + 3S_{(g)}$

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    Answer: D. $2H_{2}S_{(s)} + SO_{{2}{(g)}} \to 2HO_{2} + 3S_{(g)}$

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

16. 16.

    What is the total number of shared pair of electrons in the compound above?

    1. A.5
    2. B.8
    3. C.10
    4. D.12

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    Answer: D. 12

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17. 17.

    The preferential discharge of ions during electrolysis is influenced by the

    1. A.mechanism of electrolysis
    2. B.electrolytic reactions
    3. C.nature of the electrode
    4. D.type of electrolytic cell

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    Answer: C. nature of the electrode

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18. 18.

    Which of the following raw materials is used in the plastic industry?

    1. A.Ethene
    2. B.Methane
    3. C.Sulphur
    4. D.Hydrogen

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    Answer: A. Ethene

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19. 19.

    The most suitable substance for putting out petrol fire is

    1. A.water
    2. B.carbon(IV) oxide
    3. C.fire blanket
    4. D.sand

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    Answer: B. carbon(IV) oxide

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20. 20.

    The following factors would contribute to environmental pollution except

    1. A.production of ammonia
    2. B.manufacture of cement
    3. C.photosynthesis
    4. D.combustion

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    Answer: C. photosynthesis

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21. 21.

    The position of equilibrium in a reversible reaction is affected by

    1. A.particle size of the reactants
    2. B.vigorous stirring of the reaction mixture
    3. C.presence of a catalyst
    4. D.change in concentration of the reactants

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    Answer: D. change in concentration of the reactants

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22. 22.

    In which of the following compounds does hydrogen form ionic compounds?

    1. A.CH$_{4}$
    2. B.HCl
    3. C.NH$_{3}$
    4. D.NaH

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    Answer: D. NaH

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23. 23.

    When a salt is added to its saturated solution, the salt

    1. A.dissolves and the solution becomes super saturated
    2. B.dissolves and the solution becomes unsaturated
    3. C.precipitates and the solution remains unchanged
    4. D.dissolves and crystals are formed

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    Answer: C. precipitates and the solution remains unchanged

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24. 24.

    A reaction is endothermic if the

    1. A.reaction vessel feels cool during the reaction
    2. B.enthalpy change is negative
    3. C.bond forming energy exceeds bond breaking energy
    4. D.heat of formation of reactants exceeds heat of formation of products

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    Answer: A. reaction vessel feels cool during the reaction

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25. 25.

    The process of extraction of iron from its ore is

    1. A.decomposition
    2. B.oxidation
    3. C.reduction
    4. D.sublimation

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    Answer: C. reduction

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26. 26.

    The atomic number of an isotope of hydrogen is equal to its mass number because it

    1. A.has a totally filled valence shell
    2. B.has a high charge to mass ratio
    3. C.does not contain neutrons
    4. D.exhibits isotopy

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    Answer: C. does not contain neutrons

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27. 27.

    The change in the oxidation state of iron in the reaction represented by the equation:  $2FeCl_{3} + H_{2}S \to 2FeCl_{2} + 2HCl + S$  is

    1. A.+2 to +3
    2. B.0 to +2
    3. C.+3 to +2
    4. D.+3 to 0

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    Answer: C. +3 to +2

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28. 28.

    Atoms are electrically neutral because they

    1. A.do not conduct electricity
    2. B.contain equal number of protons and electrons
    3. C.are composed of neutrons and electrons
    4. D.cannot be attracted by electromagnetic field.

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    Answer: B. contain equal number of protons and electrons

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29. 29.

    When chlorine is passed through a sample of water, the pH of the water sample would be

    1. A.< 7
    2. B.> 7
    3. C.= 7
    4. D.0

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    Answer: A. < 7

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30. 30.

    At what temperature does the solubility of $KNO_{3}$  equal that of $NaNO_{3}$?

    1. A.0°C
    2. B.20°C
    3. C.30°C
    4. D.40°C

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    Answer: D. 40°C

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31. 31.

    Consider the following equilibrium reaction: $2AB_{{2}{(g)}} + B_{{2}{(g)}} \to 2AB_{{3}{(g)}}$. $\Delta H= -X kJmol^{-1}$. The backward reaction will be favored by

    1. A.a decrease in pressure
    2. B.an increase in pressure
    3. C.a decrease in temperature
    4. D.an introduction of a positive catalyst

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    Answer: A. a decrease in pressure

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32. 32.

    The bonding pair of electrons in a Hydrogen Chloride molecule is pulled towards the chlorine atom because

    1. A.chlorine has a larger atomic size
    2. B.chlorine has a larger atomic mass
    3. C.chlorine is more electronegative
    4. D.there is no bonding orbitals within the hydrogen atom

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    Answer: C. chlorine is more electronegative

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33. 33.

    Pure water can be made to boil at a temperature lower than 100°C by

    1. A.reducing its quantity
    2. B.decreasing the external pressure
    3. C.distilling it
    4. D.increasing the external pressure

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    Answer: B. decreasing the external pressure

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34. 34.

    The strength of metallic bonds depends on the

    1. A.charge density of the atoms
    2. B.ductility of the metal
    3. C.number of valence electrons
    4. D.total number of electrons in the atom

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    Answer: C. number of valence electrons

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35. 35.

    Analysis of a hydrocarbon shows that it contains 0.93g of Carbon per gram of the compound. The mole ratio of carbon to hydrogen in the compound is [H = 1.0, C=12.0]

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

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    Answer: A. 1:1

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36. 36.

    The number of Hydrogen ions in 1.0$dm^{3}$ of 0.02$moldm^{-3}$ tetraoxosulphate(VI) acid is   $[N_{A} = 6.02 \times 10^{23}]$

    1. A.$1.2 \times 10^{22}$
    2. B.$1.2 \times 10^{23}$
    3. C.$2.4 \times 10^{22}$
    4. D.$2.4 \times 10^{23}$

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    Answer: C. $2.4 \times 10^{22}$

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37. 37.

    Which of the following statements best explains the difference between a gas and a vapour?

    1. A.Unlike gases, vapours are liquids at room temperature
    2. B.Unlike gases, vapour can easily be condensed into liquids
    3. C.Unlike gases, vapour is readily converted into solids
    4. D.Vapours are generally denser than gases

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    Answer: B. Unlike gases, vapour can easily be condensed into liquids

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38. 38.

    How many atoms are contained in 0.2moles of nitrogen? $[N_{A} = 6.02 \times 10^{23}]$

    1. A.$1.20 \times 10^{23}$
    2. B.$2.41 \times 10^{23}$
    3. C.$3.62 \times 10^{23}$
    4. D.$4.82 \times 10^{23}$

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    Answer: B. $2.41 \times 10^{23}$

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39. 39.

    What is the mass of solute in 500$cm^{3}$ of 0.005$moldm^{-3}$ $H_{2}SO_{4}$? ( H = 1, S = 32.0, O=16.0)

    1. A.0.490g
    2. B.0.049g
    3. C.0.245g
    4. D.0.0245g

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    Answer: C. 0.245g

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40. 40.

    Consider the following reaction equation: $2HCl + Ca(OH)_{2} \to CaCl_{2} + H_{2}O$. What is the volume of 0.1$moldm^{-3}$ HCl that would completely neutralize 25$cm^{3}$ of 0.3$moldm^{-3}$ Ca(OH)$_{2}$?

    1. A.150$cm^{3}$
    2. B.75$cm^{3}$
    3. C.30$cm^{3}$
    4. D.25$cm^{3}$

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    Answer: A. 150$cm^{3}$

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41. 41.

    $Cu$ and $HNO_{3}$ are not suitable for preparing hydrogen gas because of their

    1. A.reactivity and oxidation respectively
    2. B.conductivity and corrosiveness respectively
    3. C.melting point and reduction respectively
    4. D.electronegativity and solubility respectively

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    Answer: A. reactivity and oxidation respectively

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42. 42.

    Ethene is produced from ethanol by

    1. A.decomposition
    2. B.hydrolysis
    3. C.ozonolysis
    4. D.dehydration

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    Answer: D. dehydration

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43. 43.

    Which of the following CANNOT be an empirical formula?

    1. A.$CH$
    2. B.$CH_{2}$
    3. C.$P_{2}O_{5}$
    4. D.$N_{2}O_{4}$

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    Answer: D. $N_{2}O_{4}$

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44. 44.

    Which of the following organic compounds can undergo both addition and substitution reactions?

    1. A.Pentane
    2. B.Benzene
    3. C.Propane
    4. D.Hexane

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    Answer: B. Benzene

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45. 45.

    When zinc is added to AgNO$_{3}$ solution, crystals of silver forms on the zinc surface. This indicates that zinc is

    1. A.oxidised
    2. B.reduced
    3. C.decomposed
    4. D.dissociated

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    Answer: A. oxidised

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46. 46.

    What is the solubility of a salt if 0.4g of it is obtained on evaporating 200$cm^{3}$ of its saturated solution to dryness?

    1. A.0.08$gdm^{-3}$
    2. B.2.00$gdm^{-3}$
    3. C.8.00$gdm^{-3}$
    4. D.80.00$gdm^{-3}$

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    Answer: B. 2.00$gdm^{-3}$

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47. 47.

    When substance X was added to a solution of bromine water, the solution became colourless. X is likely to be

    1. A.propane
    2. B.propanoic acid
    3. C.propyne
    4. D.propanol

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    Answer: C. propyne

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48. 48.

    Which of the following statements is true about ionic radius? Ionic radius

    1. A.increases as nuclear charge increases
    2. B.decreases as nuclear charge increases
    3. C.decreases as nuclear charge decreases
    4. D.remains constant as nuclear charge increases

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    Answer: B. decreases as nuclear charge increases

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49. 49.

    Consider the following reaction equation: $Br_{2} + 2KI \to 2KBr + I_{2}$. Bromine is acting as

    1. A.an oxidizing agent
    2. B.a reducing agent
    3. C.an acid
    4. D.a base

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    Answer: A. an oxidizing agent

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50. 50.

    The law of definite proportions states that

    1. A.pure samples of the same compound contain the same elements combined in the same proportion by mass
    2. B.pure samples of substances are in the same proportion by mass
    3. C.chemical compounds are pure because they contain the same elements
    4. D.matter can neither be created nor destroyed.

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    Answer: A. pure samples of the same compound contain the same elements combined in the same proportion by mass

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