1. CuSO4 + H2S = CuS + H2SO4
(Cu)2+ + H2S = CuS + 2(H)+
2. Fe(OH)3 + 3HNO3 = Fe(NO3)3 + 3H2O
Fe(OH)3 + 3(H)+ = (Fe)3+ + 3H2O
3. H2CO3 + 2NaOH = Na2CO3 + 2H2O
2(H)+ + 2(OH)- = 2H2O
4. Fe(NO3)2 + 2KOH = Fe(OH)2 + 2KNO3
(Fe)2+ + 2(OH)- = Fe(OH)2
5. CH3COOH + KOH = CH3COOK + H2O
(H)+ + (OH)- = H2O
6. 2KCN + H2SO4 = K2SO4 + 2HCN
2(CN)- + 2(H)+ = 2HCN