Assume the following reaction is carried out in acidic medium.
6e− + Cr2O72− ⟶2 Cr3+ + 7H2O
How many H+ do we need to add to the LHS to balance the H atoms?
14
Count number of Hydrogen on right hand side 7 ×2 = 14
Hence, add 14 H+ ions to the side which is deficient.
Cr2O72−+6e−+14H+⟶ 2{Cr}^{3+} + 7H_2O\)