WAEC Past Questions & Answer: CHEMISTRY 2018

Welcome to our WAEC past question and answer series. In this post, we will be sharing Chemistry 2018 past questions and their answers for various subjects. Stay tuned enjoy while learning.

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

A. Ethene
B. Methane
C. Sulphur
D. Hydrogen

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

A. Pentane
B. Benzene
C. Propane
D. Hexane

3. Which of the following equations represents a redox reaction?

A. HNO3(aq)+NaOH(aq)→NaNO3(aq)+H2O(l)
B. AgNO3(aq)+KCl(aq)→AgCl(s)+KNO3(aq)
C. CaCO3(s)→CaO(s)+CO2(g)
D. 2H2S(s)+SO2(g)→2HO2+3S(g)

4. The process of extraction of iron from its ore is

A. decomposition
B. oxidation
C. reduction
D. sublimation

5. What is the solubility of a salt if 0.4g of it is obtained on evaporating 200cm3 of its saturated solution to dryness?

A. 0.08gdm−3
B. 2.00gdm−3
C. 8.00gdm−3
D. 80.00gdm−3

6. An acidic salt has

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

7. A reaction is endothermic if the

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

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

A. CH4
B. HCl
C. NH3
D. NaH

9. An organic compound has the empirical formula CH2. If its molar mass is 42gmol−1, what is its molecular formula? (C = 12.0, H = 1.0)

A. C2H4
B. C3H4
C. C3H6
D. C4H8

10. Consider the following reaction equation: Br2+2KI→2KBr+I2. Bromine is acting as

A. an oxidising agent
B. a reducing agent
C. an acid
D. a base

11. Ethene is produced from ethanol by

A. decomposition
B. hydrolysis
C. ozonolysis
D. dehydration

12. Consider the following equilibrium reaction: 2AB2(g)+B2(g)→2AB3(g). ΔH=−XkJmol−1. The backward reaction will be favoured by

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

13. What is the mass of solute in 500cm3 of 0.005moldm−3 H2SO4? ( H = 1, S = 32.0, O=16.0)

A. 0.490g
B. 0.049g
C. 0.245g
D. 0.0245g

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

A. reducing its quantity
B. decreasing the external pressure
C. distilling it
D. increasing the external pressure

15
At what temperature does the solubility of KNO3 equal that of NaNO3?

A. 0°C
B. 20°C
C. 30°C
D. 40°C

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

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

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

A. propane
B. propanoic acid
C. propyne
D. propanol

18. The preferential discharge of ions during electrolysis is influenced by the

A. mechanism of electrolysis
B. electrolytic reactions
C. nature of the electrode
D. type of electrolytic cell

19. The valence electrons of 12Mg are in the

A. 3s orbital
B. 2px
C. 2s orbital
D. 1s orbital

20. Stainless steel is an alloy comprising of

A. Fe and C
B. Fe and Ni
C. Fe, C and Ni
D. Fe, C and Al

21. The number of Hydrogen ions in 1.0dm3 of 0.02moldm−3 tetraoxosulphate(VI) acid is [NA=6.02×1023]\

A. 1.2×1022
B. 1.2×1023
C. 2.4×1022
D. 2.4×1023

22. The most suitable substance for putting out petrol fire is

A. water
B. carbon(IV) oxide
C. fire blanket
D. sand

23. The following factors would contribute to environmental pollution except

A. production of ammonia
B. manufacture of cement
C. photosynthesis
D. combustion

24. The position of equilibrium in a reversible reaction is affected by

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

25
The diagram above illustrates a conical flask containing water and ice. Which of the following is correct about the diagram?

A. The water is at lower temperature than the ice
B. Energy is absorbed when the ice changes to water
C. Energy is released when the ice changes to water
D. The water molecules vibrate about a fixed point

 

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

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

27. Consider the following reaction equation: 2HCl+Ca(OH)2→CaCl2+H2O. What is the volume of 0.1moldm−3 HCl that would completely neutralize 25cm3 of 0.3moldm−3 Ca(OH)2?

A. 150cm3
B. 75cm3
C. 30cm3
D. 25cm3

28. Cu and HNO3 are not suitable for preparing hydrogen gas because of their

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

29. Which of the following CANNOT be an empirical formula?

A. CH
B. CH2
C. P2O5
D. N2O4

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

A. heat capacity
B. boiling point
C. mass
D. colour

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

A. < 7
B. > 7
C. = 7
D. 0

32. How many atoms are contained in 0.2moles of nitrogen? [NA=6.02×1023]

A. 1.20×1023
B. 2.41×1023
C. 3.62×1023
D. 4.82×1023

33. The strength of metallic bonds depends on the

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

34. When zinc is added to AgNO3 solution, crystals of silver forms on the zinc surface. This indicates that zinc is

A. oxidised
B. reduced
C. decomposed
D. dissociated

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

A. Cu2O
B. CuO
C. CuO2
D. CuO4

36. The change in the oxidation state of iron in the reaction represented by the equation: 2FeCl3+H2S→2FeCl2+2HCl+S is

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

37. Which of the following methods can be used to separate blood cells from plasma?

A. Centrifugation
B. Filtration
C. Chromatography
D. Distillation

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

A. increases as nuclear charge increases
B. decreases as nuclear charge increases
C. decreases as nuclear charge decreases
D. remains constant as nuclear charge increases

39. 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]

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

40. The law of definite proportions states that

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

41. What is the relative molecular mass of a compound which has empirical formula CH2O? [C= 12, H= 1, O= 16]

A. 42
B. 45
C. 126
D. 180

42. Atoms are electrically neutral because they

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

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

A. Solubility in water
B. Melting point
C. Relative density
D. Crystalline nature

44. Which of the following electron configurations represents the transition element Chromium 24Cr?

A. 1s22s22p63s23p64s23d4
B. 1s22s22p63s23p63d6
C. 1s22s22p63s23d44s1
D. 1s22s22p63s23p64s13d5

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

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

46
What is the total number of shared pair of electrons in the compound above?

A. 5
B. 8
C. 10
D. 12

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

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

48. The solubility of CO2 in water can be accounted for by

A. Van der Waal’s forces
B. Ionic attraction
C. dipole attraction
D. covalent bonding

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

A. Electronegativity
B. Electron Affinity
C. Ionisation potential
D. Catalytic ability

50. Particles in a solid exhibit

A. vibrational motion
B. vibrational and translational motion
C. vibrational and random motion
D. random and translational motion

Answers To Questions

1. A
2. B
3. D
4. C
5. B
6. C
7. A
8. D
9. C
10. A
11. D
12. A
13. A
14. B
15. B
16. C
17. C
18. C
19. A
20. C
21. A
22. B
23. C
24. D
25. B
26. B
27. A
28. A
29. D
30. B
31. A
32. A
33. C
34. A
35. B
36. C
37. A
38. B
39. A
40. A
41. D
42. B
43. B
44. D
45. C
46. D
47. C
48. A
49. D
50. A