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WAEC WASSCE Chemistry 2005 past questions and answers

This 2005 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 2005 set with instant marking.

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Sample WAEC WASSCE Chemistry 2005 questions

1. Which statement best describes the formation of sodium chloride from sodium and chlorine atoms?
  1. A sodium atom transfers one electron to a chlorine atom.
  2. A sodium atom shares two electrons with a chlorine atom.
  3. A chlorine atom transfers one electron to a sodium atom.
  4. The atoms share one pair of electrons equally.

Answer: A. A sodium atom transfers one electron to a chlorine atom.

Sodium loses one electron to form Na+ while chlorine gains it to form Cl−.

2. Why does water have a higher boiling point than hydrogen sulfide, H2S, despite their similar relative molecular masses?
  1. Water molecules have weaker covalent bonds.
  2. Water molecules form strong intermolecular hydrogen bonds.
  3. Water is an ionic compound at room temperature.
  4. Hydrogen sulfide molecules are larger and more polar.

Answer: B. Water molecules form strong intermolecular hydrogen bonds.

The hydrogen bonds between water molecules require substantial energy to overcome during boiling.

3. A gas occupies 100 cm3 at 100 kPa and constant temperature; what volume will it occupy at 200 kPa?
  1. 200 cm3
  2. 100 cm3
  3. 50 cm3
  4. 25 cm3

Answer: C. 50 cm3

By Boyle's law, P1V1 = P2V2, so V2 = (100 × 100)/200 = 50 cm3.

4. Assuming a molar gas volume of 22.4 dm3 at standard temperature and pressure, how many moles are in 11.2 dm3 of a gas?
  1. 2.00 mol
  2. 1.00 mol
  3. 0.25 mol
  4. 0.50 mol

Answer: D. 0.50 mol

The amount is 11.2/22.4 = 0.50 mol.

5. A salt has solubilities of 110 g per 100 g water at 60°C and 32 g per 100 g water at 20°C; how much salt crystallizes when a saturated solution containing 100 g water is cooled from 60°C to 20°C?
  1. 78 g
  2. 32 g
  3. 110 g
  4. 142 g

Answer: A. 78 g

The decrease in solubility is 110 − 32 = 78 g per 100 g water.

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