How do I complete and balance the half reaction of a redox reaction under acidic conditions?

H2SO3(aq) --%26gt;SO4^2- is the reaction which is under acidic conditions that I am trying to balance. How do I do this?|||count up the number of oxygen atoms on the left and on the right and add H2O to the side deficient in oxygen





H2SO3 + H2O = SO42-





count up the number of hydrogen atoms on the left and on the right and add H+ to the side deficient in hydrogen





H2SO3 + H2O = SO42- + 4 H+





count up the net charge on the left and on the right and add electrons to the side deficient in negative charge





H2SO3 + H2O = SO42- + 4 H+ + 2e-





If the reaction occurs under acidic conditions that is all


If the reaction is specified to be in basic solution add to each side enought OH- to cancel the H+ appearing in the half reaction. Combine H+ and OH- and cancel H2O duplication





H2SO3 + + 4 OH- = SO42- + 3 H2O + 2e-