Q. How to balance the redox reaction?

To balance a redox reaction ,

divide the given eqn. in two halves. 1-Oxidation half and 2- Reduction half 

in both half equation first of all balance all the elements other than Hydrogen and Oxygen .

now to add

1-Oxgen atom add required no. of  H₂O atoms to reactant side and balance the excess Hydrogen by adding H⁺ to the product side ...

2- Hydrogen atom add required no. of H⁺ ions to reactants side .. 

Now, after balancing the elements  ..

Balance the charge on both reactants and products side .. by adding required e^- to the required side of the equation.

Do the same with the other half equation

Multiply the both equation with an integer so that the no. of e^- on the reactants  and the product side of the added equation cancels each other .. remove all the extra molecules for eg. if there is 6 H2O molecules on reactants side or product side and  4 H20 molecules on the other side then cancel it and write away 2 H20 on the first side .. (i.e. where the 6H20 was before).

For example :- Start with a easy one !