Question

For each of the following chemical reactions, discuss the change in oxidation number of the metal atom: Cr₂O₃+3CO → 2Cr+3CO₂

1) O is reduced from +2 to -1
2) Cr is reduced from +2 to 0
3) Cr is reduced from +3 to 0
4) Cr is reduced from 0 to +3

Answer 1

Chromium in the reaction Cr2O3 + 3CO → 2Cr + 3CO2 is reduced from an oxidation state of +3 to 0. Carbon in CO is oxidized, with its oxidation number increasing from +2 to +4. Option 3, 'Cr is reduced from +3 to 0,' correctly describes the change for chromium.

Step-by-step explanation:

In the chemical reaction Cr2O3 + 3CO → 2Cr + 3CO2, we are discussing the change in oxidation number of the metal atom, specifically chromium (Cr). Chromium in Cr2O3 has an initial oxidation number of +3. During the reaction, chromium is reduced from +3 to 0, indicating it gains electrons.

On the other hand, carbon in CO is oxidized; its oxidation number increases from +2 (as in CO) to +4 in CO2. The change in carbon's oxidation number is a result of losing electrons, as it acts as the reducing agent.

Option 3, stating "Cr is reduced from +3 to 0," is correct regarding the change in the chromium's oxidation state in this reaction. It is important to balance the redox equation to ensure that the number of electrons lost in oxidation equals the number gained in reduction. In this example, carbon as the reducing agent supplies electrons to the chromium, which is being reduced.