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WAEC WASSCE Chemistry 2025 past questions and answers

This 2025 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 2025 set with instant marking.

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Sample WAEC WASSCE Chemistry 2025 questions

1. A student bubbles but-1-ene through bromine water. What observation is expected?
  1. A blue precipitate forms
  2. The orange-brown colour disappears
  3. A silver mirror forms
  4. A pungent gas is evolved

Answer: B. The orange-brown colour disappears

The carbon-carbon double bond in but-1-ene adds bromine, removing bromine water's colour.

2. Which pair of substances reacts on warming with concentrated H2SO4 to form ethyl ethanoate?
  1. Ethene and water
  2. Ethanal and hydrogen
  3. Ethanol and ethanoic acid
  4. Ethane and carbon dioxide

Answer: C. Ethanol and ethanoic acid

Ethanol reacts with ethanoic acid in an acid-catalysed esterification to produce ethyl ethanoate and water.

3. Why does a synthetic detergent usually lather better than soap in hard water?
  1. Its calcium and magnesium salts are generally soluble
  2. It removes all dissolved calcium ions by oxidation
  3. It converts hard water into distilled water
  4. It reacts with water to produce oxygen

Answer: A. Its calcium and magnesium salts are generally soluble

Unlike soap scum, the calcium and magnesium salts of many synthetic detergents remain soluble.

4. Which polymer is formed when many ethene molecules join by addition polymerisation?
  1. Nylon
  2. Starch
  3. Polyester
  4. Polyethene

Answer: D. Polyethene

Addition of ethene molecules across their double bonds forms the repeating chain in polyethene.

5. Crude petroleum is separated into fractions mainly because its components have different
  1. boiling-point ranges
  2. atomic numbers
  3. electrical charges
  4. densities of nuclei

Answer: A. boiling-point ranges

The hydrocarbons in crude petroleum have different boiling points and therefore condense at different column levels.

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