Write chemical equations for the following reactions: (i) When zinc carbonate is calcined. (ii) When manganese dioxide is heated with aluminium powder. (iii) When magnesium is treated with very dilute nitric acid.

(i) When Zinc carbonate is calcined :
ZnCo₃ ⟶ ZnO + CO₂↑
(ii) When manganese dioxide is heated with aluminum powder:
3MnO₂ + 4A1 ⟶ 3Mn + 2A1₂O₃
(iii) When magnesium is heated with very dil. HNO₃:
Mg + 2HNO₃ ⟶ Mg(NO₃)₂ + H₂