Question

How can we balance a redox reaction with half reaction method?

Answer 1

To balance a redox reaction two methods are used:
Half reaction method and ion method (both are same):
1. Balance O using H2O molecules (by adding them in either reactant or product side)
2.To balance H, add H+ ion on either side of the reactant and product.
3. Balance the change by adding electron on the side which has more +ve charge.

Answer 2

1. Firstly we have to divide the equation as Half oxidation (OHR) and Half reduction reactions (RHR) (same step for both acidic and basic medium)
2. We have to balance the elements of given equation except Hydrogen and Oxygen on both OHR and RHR (same step for both acidic and basic medium)
3. Next we have to balance the oxygens by adding the H2O molecules that how much will decrease on the side when we compare with other side. We have to add them on the side on which the Oxygens are low on Both RHR and OHR. (same step for both acidic and basic medium)
4. In acidic medium, we have to see the side in which the Hydrogen ions are high. The no.of hydrogen ions are high, that much ions H+ ions have to add on other side in both RHR and OHR but In basic medium, we have to add the no. of H ions present in the equation, that much OH- ions have to add on the side where H ions are high and the other side we have to add the no.of H ions greater that much H2O ions ave to be add on other side. *(different step for both acidic and basic medium) so have a careful look
5. Next we have to see the remaining ions after calculate on both sides of OHR and RHR and have to add the to the side where there will remains more electrons after calculating the ions of LHS and RHS of both OHR and RHR.(same step for both acidic and basic medium)
6. Next we have to balance the electrons on that we should have same in both OHR and RHR. (same step for both acidic and basic medium)
7. After electrons being balanced, we have to calculate the no.of OH- (in basic medium)/ no. of H+ (in acidic) and total no.of H2O remains after subracting one from other by combining both RHR and OHR and have t write the on wich side the more are remained. (slight difference for both acidic and basic medium on calculating H+ in acidic and OH- in basic)
8. At last we have to add both the LHS parts of OHR and RHR and RHS of both. (same step for both acidic and basic medium)
9. thus the equation is balanced