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WAEC WASSCE Chemistry 2023 past questions and answers

This 2023 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 2023 set with instant marking.

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Sample WAEC WASSCE Chemistry 2023 questions

1. Aqueous copper(II) sulfate is electrolysed using inert electrodes. Which substance is formed at the cathode?
  1. Copper
  2. Oxygen
  3. Hydrogen
  4. Sulfur dioxide

Answer: A. Copper

Copper(II) ions gain electrons at the cathode and are deposited as copper metal.

2. A charge that supplies 0.50 mol of electrons is passed through silver nitrate solution. What mass of silver is deposited? (Ag = 108)
  1. 27 g
  2. 54 g
  3. 108 g
  4. 216 g

Answer: B. 54 g

Each Ag+ ion requires one electron, so 0.50 mol of electrons deposits 0.50 mol or 54 g of silver.

3. In a cell made from Zn|Zn2+ and Cu2+|Cu half-cells, which electrode is the anode when the cell produces electricity?
  1. The copper electrode, where copper ions gain electrons
  2. The salt bridge, where ions are discharged
  3. The zinc electrode, where zinc atoms lose electrons
  4. The copper electrode, where copper atoms lose electrons

Answer: C. The zinc electrode, where zinc atoms lose electrons

Oxidation occurs at the anode, and zinc atoms are oxidized to Zn2+ ions in this cell.

4. A steel ship's hull is protected from corrosion by attaching blocks of magnesium to it. How does the magnesium protect the steel?
  1. It forms a waterproof coating over the whole hull
  2. It neutralizes all the oxygen in seawater
  3. It makes the steel an inert metal
  4. It oxidizes preferentially and acts as a sacrificial metal

Answer: D. It oxidizes preferentially and acts as a sacrificial metal

Magnesium is more reactive than iron and corrodes preferentially, supplying protection to the steel.

5. What is the general trend in the boiling points of straight-chain alkanes as their molecular masses increase?
  1. They generally increase because intermolecular dispersion forces become stronger
  2. They generally decrease because covalent bonds become weaker
  3. They remain constant because all alkanes are non-polar
  4. They become zero when the chains contain more than four carbon atoms

Answer: A. They generally increase because intermolecular dispersion forces become stronger

Larger alkane molecules have stronger dispersion forces, so more energy is needed to separate them.

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