1) H2, C, Ba, O2, Cl2
2) Cu(+2)O(-2), Fe(+2)OH(-2), H(+)N(+5)O(-2), K(+1)Cr(+6)O(-2)
3) S(0) - 4ē = S(+4)
Cr(+3) - 3ē = Cr(+6)
Cl2(0) + 1ē = 2Cl(-)
Mn(+7) + 3ē = Mn(+4)
H2(0) - 1ē = 2H(+)
O(-) + 1ē = O(-2)
S(+6) + 8ē = S(-2)
P(0) - 5ē = P(+5)
O2(0) + 2ē = 2O(-2)
2F(-) - 1ē = F2(0)