Question

How many electrons are transferred
Cr + MnO4^- + 2H2O = MnO2 + Cr(OH)3 + OH^-

Answer 1

what was the oxidation state change for, both, Cr and Mn?

Answer 2

Cr = 0 Cr = +3
Mn = +7 Mn=+4

What about OH- and H2O

Answer 3

water and OH^- didn't change oxidation states, so no electrons were transferred, they didn't participate in the redox reaction.

so Cr lost 3 electrons and Mn gained 3 electrons.

So 3 electrons were transferred