Răspuns:
a) 3P+ 5HNO3 +2H2O =>5NO+3H3PO4
P⁰ - 5e- => P⁵ (oxidareagent reducator)×3
N⁵ + 3e- =>N² (reducereagent oxidant)×5
P⁰ - 15e- => P⁵
N⁵ + 15e- =>N²
b) S+2 HNO3 ----> 2NO + H2SO4
S⁰ - 6 e- => S⁶ (oxidareagent reducator )
2 N⁵ + 6 e- => 2 N³(reducere agent oxidant)
c) 2 KMnO4 + 6 HCl + 5 H2S =>2 KCl + 2 MnCl2 + S + 8H2O
2 Mn⁷ + 10 e- => 2 Mn²(reducere agent oxidant )
5 S-² - 10 e- => 5 S⁰ (oxidareagent reducator )
