Explanation:
A balanced redox chemical equation is an equation that contains same number of atoms on both reactant and product side. Also, it contains same total charge on reactant and product side.
For example, [tex]MnO^{-}_{4}(aq) + Ag(s) + H^{+}(aq) \rightarrow Mn^{2+}(aq) + Ag^{+}(aq) + H_{2}O(l)[/tex]
Number of atoms on reactant side are as follows.
Mn = 1
O = 4
Ag = 1
H = 1
Number of atoms on product side are as follows.
Mn = 1
O = 1
Ag = 1
H = 2
Therefore, to balance the equation multiply [tex]H^{+}(aq)[/tex] on reactant side by 8 and multiply [tex]H_{2}O[/tex] on product side by 4.
[tex]MnO^{-}_{4}(aq) + Ag(s) + 8H^{+}(aq) \rightarrow Mn^{2+}(aq) + Ag^{+}(aq) + 4H_{2}O(l)[/tex]
Now, total charge on reactant side is +7 but total charge on product side is +2. Therefore, to balance the charges we multiply Ag(s) on reactant side by 5 and [tex]Ag^{+}[/tex] on product side by 5.
Therefore, completely balanced redox reaction equation will be as follows.
[tex]MnO^{-}_{4}(aq) + 5Ag(s) + 8H^{+}(aq) \rightarrow Mn^{2+}(aq) + 5Ag^{+}(aq) + 4H_{2}O(l)[/tex]