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WAEC WASSCE Chemistry 2019 past questions and answers

This 2019 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 2019 set with instant marking.

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Sample WAEC WASSCE Chemistry 2019 questions

1. What amount, in moles, is contained in 5.6 dm3 of an ideal gas at standard temperature and pressure, where the molar gas volume is 22.4 dm3 mol-1?
  1. 0.25 mol
  2. 0.50 mol
  3. 0.10 mol
  4. 4.00 mol

Answer: A. 0.25 mol

The amount is volume divided by molar gas volume, so 5.6/22.4 = 0.25 mol.

2. A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass; what is its empirical formula?
  1. C2H4O2
  2. CH2O
  3. CHO
  4. C2H2O

Answer: B. CH2O

Dividing the percentages by the relative atomic masses gives the simplest mole ratio C:H:O of 1:2:1.

3. An element consists of 75% atoms of mass 35 and 25% atoms of mass 37; what is its relative atomic mass?
  1. 35.0
  2. 36.0
  3. 35.5
  4. 37.0

Answer: C. 35.5

The weighted mean is (0.75 x 35) + (0.25 x 37) = 35.5.

4. Which method is most suitable for separating two miscible liquids with different boiling points?
  1. Filtration
  2. Separating funnel
  3. Crystallization
  4. Fractional distillation

Answer: D. Fractional distillation

Fractional distillation separates miscible liquids by their different boiling points.

5. What volume is occupied by 2.0 mol of an ideal gas at room temperature and pressure if the molar gas volume is 24 dm3 mol-1?
  1. 48 dm3
  2. 12 dm3
  3. 24 dm3
  4. 0.083 dm3

Answer: A. 48 dm3

The volume is amount multiplied by molar gas volume, giving 2.0 x 24 = 48 dm3.

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