Question

Determine the oxidizing agent in the following reaction. Ni(s) + 2 AgClO4(aq) → Ni(ClO4)2(aq) + 2 Ag(s)

Answer 1

Silver perchlorate $\text{AgClO}_4$ serves as the oxidizing agent in this reaction.

Explanation

Both silver perchlorate $\text{AgClO}_4$ in the reactants and nickel (II) perchlorate $\text{Ni}(\text{ClO}_4)_2$ in the products exists as ionic salt dissolved in an aqueous solution. Rewriting the chemical equation as an ionic one might help eliminate spectator ions and make changes in oxidation states more apparent.

Ionic equation:

$\text{Ni} \; (s) + 2 \; \text{Ag}^{+} \; (aq) + 2\; \text{ClO}_4 \; (aq) \to \text{Ni}^{2+} \; (aq) + 2\; \text{ClO}_4^{-} \; (aq) + 2 \; \text{Ag} \; (aq)$

Two perchlorate ions are present on both sides of the equation. These ions act as spectator ions that take no part in the overall reaction. Thus it is possible to determine the oxidizing and reducing agent without knowing the oxidation state of atoms in the perchlorate ion. Marking oxidation states on top of each element gives the following equation:

$\stackrel{0}{\text{Ni}} \; (s) + 2 \; \stackrel{+1}{\text{Ag}^{+}} \; (aq)\to \stackrel{+2}{\text{Ni}^{2+}} \; (aq) + 2 \; \stackrel{0}{\text{Ag}} \; (aq)$

There is a decrease in the oxidation state of silver, from +1 to 0. Silver atoms, therefore, gain electrons and are reduced. The reactant containing silver ions, silver perchlorate, thus acts as the oxidation agent of this reaction.