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JAMB Chemistry 1979 Question 16

Question 16

Metals and their Compounds

When ammonium, potassium and calcium carbonates are each separately heated

  1. A.none of them will decompose
  2. B.each of them will decompose to give carbondioxide and the respective oxide
  3. C.ammonium carbonate and potassium carbonate will not decompose
  4. D.only ammonium carbonate and calcium carbonate will decompose to carbondioxide and the respective oxide
  5. E.ammonium carbonate will decompose to give carbondioxide, water and ammonia.
Show the answer and explanation

Answer: E (ammonium carbonate will decompose to give carbondioxide, water and ammonia.)

Explanation

On heating, (NH4)2CO3 → 2NH3 + H2O + CO2. Calcium carbonate gives CaO and CO2, but potassium carbonate does not decompose, and ammonium carbonate gives no oxide.