a) 4NH3+7O2=4NO2+6H2O
N+3 -1e- => N+4 1
O2 +2*2e- => 2O2- 4
b)2Al+3i2=2Ali3
Al -3e- => Al3+ 2
i2 +2*1e- => 2i- 3
c)5HNO3+3P+2H2O=3H3PO4+5NO
N+5 +3e- => N+2 5
P -5e- => P+5 3
d)2KMnO4 + 16HCl = 5Cl2 + 2KCl + 2MnCl2 + 8H2O
Mn+7 +5e- =>Mn+2 2
2Cl- -1*2e- =>Cl2 5