i) Zn(s) + Ag NO3(aq) → Zn (NO3)2(aq)+ Ag(s)
Balanced equation : Zn(s) + 2 AgNO3(aq) → Zn (NO3)2(aq) + 2Ag(s)
ii) Fe2O + C(s) → Fe(s) + CO2(g)
Balanced equation : 2Fe2O3(s) + 3C(s) → 4Fe(s) + 3CO2(g)
iii) Ag(s) + H2S(g) → Ag2S(s) + H2O(I)
Balanced equation : We cannot balance the equation because atom ‘O’ does not exist in the reactants.
iv) Cu(s) + O2(g) → CuO(s)
Balanced equation : 2Cu(s) + O2(g) → 2CuO(s)