Write balanced chemical equations to explain what happens, when
(i) Mercuric oxide is heated.
(ii) Mixture of cuprous oxide and cuprous sulphide is heated.
(iii) Aluminium is reacted with manganese dioxide.
(iv) Ferric oxide is reduced with aluminium.
(v) Zinc carbonate undergoes calcination.

Explanation

(i) Mercuric oxide is heated.
`2HgO overset("Heat")to Hg+O_(2)`
Mercuric oxide decomposes to form mercury with the evolution of oxygen.
(ii) Mixture of cuprous oxide and cuprous sulphide is heated.
`2Cu_(2)O+Cu_(2)S overset("Heat")to 6Cu+SO_(2)`
Copper is formed and `SO_(2)` gas is produced.
(ii) Aluminium is reacted with manganese dioxide.
`4Al+3MnO_(2) to 2Al_(2)O_(3)+3Mn`
(iv) Ferric oxide is reduced with aluminium.
`Fe_(2)O_(3)+2Al to Al_(2)O_(3)+2Fe`
(v) Zinc carbonate undergoes calcination.
`ZnCO_(3) to ZnO+CO_(2)`