Building a half reaction
in an acid solution

Some easy steps to follow.

The permanganate ion is reduced to the manganese 2+ ion
Step 1 Write the two species on either side of an equation
Step 2 Balance all the atoms of the half equation except for oxygen and hydrogen. In this case they are balanced.
Step 3 Balance the oxygen atoms by adding water to the side deficient in oxygen atoms.
Step 4 Balance for hydrogens by adding hydrogen ions to the side deficient in in hydrogens
Step 5 Balance the charge on each side of the equation by adding electrons to the most positive side.

 
Step 6 Place the states of reactants and products.
Exercises
Continue with half cell reactions in an alkaline solution.
Continue to see how the half reactions are used to form the overall cell reaction.