which of the following are redox equations?

Question

1)2 Na + Cl2 2 NaCl
2)H2 + Cl2 2 HCl
3)NH3 + HCl NH4+ + Cl-
4)2 KClO3 2 KCl + 3 O2
5)H2SO4 + 2 KOH K2SO4 + 2 H2O
6)Zn + CuSO4 ZnSO4 + Cu
7)C + O2 CO2
8)NaCl + AgNO3 AgCl + NaNO3
9)2 H2O 2 H2 + O2

How do you know?? because i got some of them but the long equations i don't get.

Answer 1

1, 2, 4, 6, 7 and 9 are redox.
Look for any change in valency (oxidation state) of any element.