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JAMB UTME Chemistry 2025 past questions and answers

This 2025 JAMB UTME 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 JAMB UTME Chemistry 2025 questions

1. In the blast furnace, which substance directly reduces iron(III) oxide to metallic iron?
  1. Carbon dioxide
  2. Carbon monoxide
  3. Oxygen
  4. Calcium oxide

Answer: B. Carbon monoxide

Carbon monoxide removes oxygen from iron(III) oxide and is itself oxidized to carbon dioxide.

2. Which ion commonly gives its aqueous solution a blue colour?
  1. Fe2+
  2. Zn2+
  3. Al3+
  4. Cu2+

Answer: D. Cu2+

Aqueous Cu2+ ions are characteristically blue, whereas these other ions are colourless or pale green.

3. An iron pipe is buried in moist soil and connected electrically to a block of magnesium. Why does this reduce rusting of the pipe?
  1. Magnesium oxidizes preferentially and supplies electrons to the iron
  2. Magnesium forms a waterproof coating over the entire pipe
  3. Magnesium removes all oxygen from the surrounding soil
  4. Magnesium converts rust back into iron

Answer: A. Magnesium oxidizes preferentially and supplies electrons to the iron

Magnesium is more reactive than iron and acts as a sacrificial anode, corroding in preference to the pipe.

4. What is the main purpose of adding cryolite during the electrolytic extraction of aluminium from alumina?
  1. To oxidize aluminium ions at the cathode
  2. To react with carbon dioxide at the anode
  3. To lower the melting point of the electrolyte and improve its conductivity
  4. To prevent aluminium ions from being discharged

Answer: C. To lower the melting point of the electrolyte and improve its conductivity

Cryolite dissolves alumina, lowers the operating temperature and makes the molten mixture more conductive.

5. Which general formula represents an acyclic alkene containing one carbon-carbon double bond?
  1. CnH2n
  2. CnH2n+2
  3. CnH2n-2
  4. CnHn

Answer: A. CnH2n

Acyclic alkenes with one double bond have two fewer hydrogen atoms than the corresponding alkanes, giving CnH2n.

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