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WAEC WASSCE Chemistry 2004 past questions and answers

This 2004 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 2004 set with instant marking.

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Sample WAEC WASSCE Chemistry 2004 questions

1. For N2(g) + 3H2(g) ⇌ 2NH3(g), what happens to the equilibrium position when pressure is increased at constant temperature?
  1. It shifts to the right
  2. It shifts to the left
  3. It does not shift
  4. The reaction stops

Answer: A. It shifts to the right

The higher pressure favours the side with fewer gas molecules, which is the ammonia side.

2. Equal masses of powdered calcium carbonate and marble chips are separately added to excess dilute hydrochloric acid; why does the powder usually react faster?
  1. It has a higher melting point
  2. It exposes a larger surface area to the acid
  3. It produces a different salt
  4. It lowers the acid concentration less

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

Powder has a greater exposed surface area, allowing more frequent effective collisions with acid particles.

3. Which statement best describes the effect of a catalyst on a reversible reaction at equilibrium?
  1. It increases the equilibrium yield of products
  2. It changes the equilibrium constant
  3. It speeds up forward and reverse reactions without changing the equilibrium composition
  4. It is permanently consumed

Answer: C. It speeds up forward and reverse reactions without changing the equilibrium composition

A catalyst lowers the activation barrier for both directions and therefore does not alter the equilibrium composition.

4. What is the pH of 0.001 mol/dm3 hydrochloric acid, assuming complete ionization?
  1. 1
  2. 2
  3. 4
  4. 3

Answer: D. 3

The hydrogen ion concentration is 10^-3 mol/dm3, so pH = -log10(10^-3) = 3.

5. 25.0 cm3 of 0.10 mol/dm3 monoprotic acid exactly neutralizes 25.0 cm3 of sodium hydroxide; what is the sodium hydroxide concentration?
  1. 0.10 mol/dm3
  2. 0.050 mol/dm3
  3. 0.20 mol/dm3
  4. 2.50 mol/dm3

Answer: A. 0.10 mol/dm3

A monoprotic acid reacts 1:1 with NaOH, so equal titration volumes require equal concentrations.

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