Cr2O3 + H2 --> Cr + H2O

Al + Cl3 --> AlCl3

MgCl2 + AgNO3 --> Mg(NO3) + AgCl

Cr2O3 + H2 --> Cr + H2O

Al + Cl3 --> AlCl3

MgCl2 + AgNO3 --> Mg(NO3) + AgCl


The first is an oxidation reduction reaction. Cr2O3 is the oxidizer, H2 is the reducing agent. Cr2O3 is reduced, H2 is oxidized.

The second is also an oxidation reduction equation, except you have it wrong. There's no such thing as Cl_3. It should be

2\,Al + 3\,Cl2 = 2\,AlCl_3

The last is what I call a "metathetical" reaction. I think you'll probably know it as a double exchange reaction or a double decomposition reaction. Basically, the ions exchange. The "driving force" is the formation of insoluble AgCl.