130.

Balance the following chemical equation by oxidation number method:
           in acidic medium.

(i) The skeleton equation along with oxidation number of each atom is

  
(ii) Noting the change in O.N. of above atoms
Increase Zn = 0 to  +2  i.e 2
Decrease N = +5 to -3 i.e. 8

(iii) Equalise the increase/decrease O.N. by multiplying Zn by 4 and  by 1.
                
(iv) Balance Zn atoms by multiple Zn² ion by 4.
    
(v) Balance the oxygen atoms by adding three H₂O molecules on the right-hand side. 

(vi) Balancing the hydrogen atoms by adding 10H⁺ ions  on the reactant side. The complete balanced equation is