Question

given the reaction below, which is being reduced? mg + cl₂ ⟶ mg²⁺ + 2cl⁻
○ 2cl⁻
○ cl₂
○ mg
○ mg²⁺

Explanation:

1. Recall the definition of reduction: gain of electrons (or decrease in oxidation state).
2. Analyze the oxidation states:

• In $\ce{Mg}$, the oxidation state is 0. In $\ce{Mg^{2+}}$, it is +2 (oxidation, loss of electrons).
• In $\ce{Cl_{2}}$, the oxidation state of $\ce{Cl}$ is 0. In $\ce{Cl^{-}}$, it is -1 (reduction, gain of electrons).
• $\ce{2Cl^{-}}$ is a product (already reduced, not the species being reduced). $\ce{Mg^{2+}}$ is a product (oxidized form of $\ce{Mg}$).

1. Thus, $\ce{Cl_{2}}$ gains electrons (oxidation state decreases from 0 to -1) and is being reduced.

Answer:

B. $\ce{Cl_{2}}$