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WAEC WASSCE Chemistry 2008 past questions and answers

This 2008 WAEC WASSCE Chemistry set has 40 practice questions. Try these 5 free sample questions, tap a question to reveal the answer and explanation. Then practise the whole 2008 set with instant marking.

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Sample WAEC WASSCE Chemistry 2008 questions

1. A student reacts equal masses of magnesium with excess dilute hydrochloric acid, using magnesium powder in one experiment and a ribbon in another. Why does the powder react faster?
  1. It has a lower relative atomic mass.
  2. It produces a stronger acid.
  3. It exposes a larger surface area to the acid.
  4. It changes the final amount of hydrogen formed.

Answer: C. It exposes a larger surface area to the acid.

Powdered magnesium exposes more surface for collisions with acid particles per unit time.

2. For a reversible reaction at equilibrium, what is the effect of adding a suitable catalyst?
  1. It makes equilibrium establish faster without changing the equilibrium composition.
  2. It increases the equilibrium yield of products in every reaction.
  3. It stops the reverse reaction.
  4. It changes the value of the equilibrium constant.

Answer: A. It makes equilibrium establish faster without changing the equilibrium composition.

A catalyst speeds up both forward and reverse reactions equally, so the equilibrium position is unchanged.

3. A reaction releases 75 kJ of heat to its surroundings at constant pressure. What is the sign of its enthalpy change, ΔH?
  1. +75 kJ
  2. 0 kJ
  3. +150 kJ
  4. -75 kJ

Answer: D. -75 kJ

A reaction that releases heat is exothermic and has a negative enthalpy change.

4. Which statement describes a reversible reaction at dynamic equilibrium in a closed vessel?
  1. The forward reaction has stopped.
  2. The forward and reverse reactions continue at equal rates.
  3. The concentrations of reactants and products must be equal.
  4. All reactants have been converted into products.

Answer: B. The forward and reverse reactions continue at equal rates.

At dynamic equilibrium both reactions continue at equal rates, keeping concentrations constant.

5. During the electrolysis of molten sodium chloride with inert electrodes, which substance is formed at the cathode?
  1. Chlorine gas
  2. Hydrogen gas
  3. Sodium metal
  4. Sodium hydroxide

Answer: C. Sodium metal

Sodium ions gain electrons at the cathode to form sodium atoms.

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