WAEC Chemistry Questions and Answers 2020/2021 (Essay and Objectives)

WAEC Chemistry Questions and Answers 2020. In this article, you will find the 2020 WAEC Chemistry questions and answer, how the West African Examinations Council (WAEC) sets Chemistry questions and how to answer them.

It is important to understand the WAEC Chemistry questions before choosing answers. This is because some questions are so confusing such that if one is not careful, wrong answers would be mistaken for correct ones.

WAEC Chemistry Answers 2020 (Theory and Objectives)

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) Petane

(b) Benzene

(c) Propane

(d) Hexane

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

(a) AgNO_3(aq) + KCI_(aq) → AgCI_(s) + KNO_3(aq)

(b) HNO_3(aq) + NaOH_(aq) →NaOH_(aq) → NaNO_3(aq) + H2O_(l)

(c) CaCO_3(s) → CaO_(s) + CO_2(g)

(d) 2H2_S(s) + SO_2(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 of 0.4g of it is obtained on evaporating 200 cm³ of its saturated solution to dryness?

(a) 0.08 gdm^-3

(b) 2.00 gdm^-3

(c) 8.00 gdm^-3

(d) ) 80.00 gdm^-3

6. An acidic salt has

(a) 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) HCI

(c) HN₃

(d) NaH

9. Consider the following reaction equation: Br₂ + 2K1→ 2KBr + I₂. Bromine is acting as

(a) an oxidizing agent

(b) reducing agent

(c) an acid

(d) a base

10. An organic compound has the emphiical formula CH₂. If its molar mass is 42 gmol^-1, what is its molecular formula? [H=1.0, C=12.0]

(a) C₂H₄

(b) C₃H₄

(c) C₃H₆

(d) C₄H_g

11. Ethane is produced form ethanol by

(a) decomposition 

(b) hydrolysis

(c) ozonolysis

(d) dehydration

12. Consider the following equilibrium reaction: 2AB_2(g) + B_2(g) ↔ 2AB_3(g) ∆H = -X kJmol^-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 500 cm^-3of 0.00 moldm^-3 H₂SO₄? [H = 1.0, O=16.0, S=32.0]

(a) 0.490 g

(b) 0.049 g

(c) 0.245 g

(d) 0.0245 g

14. Pure water can be made to boil at temperature lower than 100^oC by

(a) Reducing its quantity

(b) decreasing the external pressure

(c) distilling it

(d) increasing the external pressure

15. Consider the following sketch of the solubility curve of some substances

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

0^oC (b) 20^oC (c) 30^oC (d) 40^oC

 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 substances 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) electrolysis reactions

(c) nature of the electrode

(d) type of electrolytic cell

19. The valence electrons of ₁₂Mg are in the

(a) 3s orbital

(b) 2P_x orbital

(c) 2_x orbital

(d) Is orbital

20. Stainless steel is an alloy comprising of

(a) Fe and C

(b) Fe and Ni

(c) Fe, C and Ni

(d) Fe and AI

21. The number of hydrogen ions in 1.0 dm³ of 0.02moldm^-3 tetraoxosulphate(VI) acid is [N_A = 6.0.2 x 10²³]

(a) 1.2 x 10²²

(b) 1.2 x 10²³

(c) 2.4 x 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 catalyst

(d) change in concentration of the reactants

25. The diagram below illustrates a conical flask containing water and ice

Which of the following statements about the diagram is correct?

(a) The water is at a 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.

WAEC Chemistry Questions and Answers 2020 Essay

Note: The questions and answers above are WAEC repeated questions on Chemistry not exactly the 2020 WAEC questions and answers.

The questions are likely WAEC Chemistry questions and they are for practice. Ensure you study them well as most questions will form part of WAEC 2020 Chemistry questions and answers.

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