KMnO4 as an oxidizer in acidic media:
MnO−4+8H++5e−→Mn2++4H2O (gained 5 electrons from reductant)
To find out the Eq.wt of any element we use the formula, Eq.wt = molar mass/ no. Of electrons lost or gained.
Therefore, Eq. wt. of grams/equivalent
KMnO4=158.045=31.61