(i) KMnO4.
Let the oxidation number of Mn=x
Writing the oxidation number of each atom at the top of its symbol,
     +1       x      -2
     K       Mn      O4
The algebraic sum of the oxidation number of various atoms = 0
(ii)Â
Let the oxidation number of Cr = x
Writing the oxidation number of each atom at the top of tis symbol,
             +1       x       -2
             K2       Cr2      O7
The algebraic sum of the oxidation number of various atoms = 0
Let the oxidation number of Cl = x
Writing the oxidation number of each atom at the top of its symbol,
           +1     x       -2
           K      Cl       O4
The algebraic sum of the oxidation number ofvarious atoms = 0