Ans: Zinc sulphide on heating in presence of air forms zinc oxide and sulphur dioxide.
  ZnS + 3 O₂ + heat → 2 ZnO + 2 SO₂
In calcination process the carbonate ore is heated strongly in the absence of air to convert it into metal oxide. As obtaining metal from metal oxide is easy process.
ZnCO₃ (on calcination) → ZnO + CO₂
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