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Which of the following chemical changes best represents calcination?

1. 2Ag + 2HCl +(O) → 2AgCl + H2O
2. 2Zn + O2 → 2ZnO
3. 2ZnS + 3O2 → 2ZnO + 2SO2
4. MgCO3 → MgO + CO2

Correct answer: MgCO3 → MgO + CO2

Solution

Calcination is heating an ore (usually a carbonate or hydroxide) in limited air to expel volatile matter, e.g. MgCO3 -> MgO + CO2. (2ZnS + 3O2 -> 2ZnO + 2SO2 is roasting; the silver reaction is not calcination.)

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