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WAEC WASSCE Chemistry 2001 past questions and answers

This 2001 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 2001 set with instant marking.

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Sample WAEC WASSCE Chemistry 2001 questions

1. A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass; what is its empirical formula?
  1. C2H4O2
  2. C2H2O
  3. CH2O
  4. CHO2

Answer: C. CH2O

For 100 g, the mole ratio C:H:O is approximately 3.33:6.7:3.33, which simplifies to 1:2:1.

2. A neutral atom has 17 protons and 18 neutrons; how many electrons does it contain?
  1. 17
  2. 18
  3. 35
  4. 1

Answer: A. 17

A neutral atom has equal numbers of protons and electrons, so it has 17 electrons.

3. Element X has the electron arrangement 2,8,7; what is the formula of the ionic compound it forms with magnesium?
  1. MgX
  2. Mg2X
  3. MgX3
  4. MgX2

Answer: D. MgX2

Magnesium forms Mg2+ ions and X forms X- ions, so two X- ions balance one Mg2+ ion.

4. Which substance consists of molecules held together by covalent bonds within each molecule?
  1. Sodium chloride
  2. Methane
  3. Magnesium oxide
  4. Potassium bromide

Answer: B. Methane

Methane is made of discrete molecules in which carbon and hydrogen share electron pairs.

5. What is the oxidation number of manganese in KMnO4?
  1. +2
  2. +4
  3. +7
  4. -1

Answer: C. +7

Potassium is +1 and four oxygen atoms total -8, so manganese must be +7 for the compound to be neutral.

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