Explain giving equation, what happens when: (a) ZnCO3 is heated in the absence of air? (b) a mixture of Cu2O and Cu2S is heated?

a0 When zinc carbonate is heated strongly in the absence of air, it decomposes to form zinc oxide and carbon dioxide.

ZnCO3(s) → ZnO(s) + CO2

(b) When copper (I) oxide reacts with copper (I) sulphide, it forms copper metal and sulphur dioxide. 2Cu2O(s) + Cu2S → 6Cu(s) + SO2(g)