Given the half-reaction is being balanced in acidic solution

CHEMISTRY · Subjective · CBSE · Chemistry · Redox Reactions · Redox Reactions

Problem

Given the half-reaction

\mathrm{MnO_4^- \rightarrow Mn^{2+}}

is being balanced in acidic solution, a student adds

4\,\mathrm{H_2O}

to the product side and

8\,\mathrm{H^+}

to the reactant side. In one or two sentences, explain how these additions conserve both mass and overall charge in the half-reaction.