How did they get 2e between ClO and Cl2 on the equation of Cr(OH)3+ClO-CrO4+Cl2
That's ClO^- + 2e ==> Cl2
Cl in 2ClO^- has an oxidation state +1 for each Cl and for 2 Cl it is +2. It goes to Cl2 with an oxidation state of zero. From +2 to zero is loss of 2e.