Răspuns:
a) 3 Ca + N2 → Ca3N2
3 Ca0 - 6 e- → 3 CaII (oxidare) agent reducator
2 N0 + 6 e- → 2 N-III (reducere) agent oxidant
b) H2SO4 + H2S → SO2 + 2 H2O + S
S-II - 2 e- → S0 (oxidare) agent reducator
S-II - 6 e- → SIV (oxidare) agent reducator
SVI + 6 e- → S0 (reducere) agent oxidant
SVI + 2 e- → SIV (reducere) agent oxidant
c) 2 KBr + Cl2 → 2 KCl + Br2
2 Br-I - 2 e- → 2 Br0 (oxidare) agent reducator
2 Cl0 + 2 e- → 2 Cl-I (reducere) agent oxidant
d) CuO + CO → Cu + CO2↑
CuII + 2 e- → Cu0 (reducere) agent oxidant
CII - 2 e- → CIV (oxidare) agent reducator
Explicație: