Question

Which element is reduced in the reaction below?
Fe₂⁺ + H⁺ + Cr₂O₇²⁻ → Fe₃⁺ + Cr₃⁺ + H₂O

Answer 1

In the given reaction, Chromium (Cr) is the element that is reduced, as indicated by the transition from Cr₂O⁷²⁻ to Cr³⁺.

Step-by-step explanation:

In the reaction Fe₂⁺ + H⁺ + Cr₂O₇²⁻ → Fe₃⁺ + Cr₃⁺ + H₂O, the element that is reduced is Chromium (Cr). During the reaction, you can observe that Cr changes from Cr₂O₇²⁻ to Cr³⁺, indicating a reduction in its oxidation state from +6 to +3.

To identify the reduction half-reaction, we can refer to the details that Cr₂O⁷²⁻ is reduced to Cr³⁺, which is accompanied by the gain of electrons, a key feature of a reduction process. Here are the half-reactions, illustrating the changes: Oxidation: 6Fe²⁺ (aq) → 6Fe³⁺ (aq) + 6e⁻.

Reduction: 6e⁻ + 14H⁺ (aq) + Cr₂O⁷²⁻ (aq) → 2Cr³⁺ (aq) + 7H₂O (1). This clearly shows that Cr₂O⁷²⁻ is the species that undergoes reduction. We know this because it has gained electrons, and the oxidation state of chromium decreases during the course of the reaction.