mam can you please tell me about redox balancing???

Balancing Redox Equations 

Let us consider an example say,

HNO₃(aq) + H₃AsO₃(aq)  -->  NO(g) + H₃AsO₄(aq) + H₂O(l)

1. First determine the oxidation numbers for the atoms in the formula and use them to decide whether the reaction is a redox reaction. In the above reaction, the N atoms change from +5 to +2, so they are reduced. As atoms, which change from +3 to +5, are oxidized. This information is enough to tell us that the reaction is redox.

2. Determine the net increase in oxidation number for the element that is oxidized and the net decrease in oxidation number for the element that is reduced.

As  +3 to +5  Net Change = +2

N  +5 to +2  Net Change = -3

3. Determine a ratio of oxidized to reduced atoms that would yield a net increase in oxidation number equal to the net decrease in oxidation number.

As atoms would yield a net increase in oxidation number of +6. (Six electrons would be lost by three arsenic atoms.)

2 N atoms would yield a net decrease of -6. (Two nitrogen atoms would gain six electrons.)

Thus the ratio of As atoms to N atoms is 3:2.

4. To get the ratio identified in Step 3, add coefficients to the formulas which contain the elements whose oxidation number is changing.

2HNO₃(aq) + 3H₃AsO₃(aq)  ------->  NO(g) + H₃AsO₄(aq) + H₂O(l)

5. Balance the rest of the equation by inspection.

2HNO₃(aq) + 3H₃AsO₃(aq)  -------->  2NO(g) + 3H₃AsO₄(aq) + H₂O(l)

Regards