Assume the following reaction is carried out in acidic medium.
6e−+Cr2O72−⟶2Cr3++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+⟶2Cr3++7H2O