Question

The equilibrium \( \text{Cr}_2\text{O}_7^{2-} \rightleftharpoons 2\text{CrO}_4^{2-} \):

• A. exists in basic medium
• B. exists in acidic medium
• C. exists in neutral medium
• D. does not exist

Hint:

The chromate-dichromate equilibrium is a classic example of Le Chatelier’s Principle, where the reaction shifts based on pH.

Answer 1

The Correct Option is A

The equilibrium between dichromate (\( \text{Cr}_2\text{O}_7^{2-} \)) and chromate (\( \text{CrO}_4^{2-} \)) ions is pH-dependent. - In an acidic medium, dichromate ions dominate. - In a basic medium, the equilibrium shifts toward chromate ions due to hydroxide ions (\( OH^- \)) removing \( H^+ \) ions from the solution. The reaction can be expressed as: \[ \text{Cr}_2\text{O}_7^{2-} + 2OH^- \rightleftharpoons 2\text{CrO}_4^{2-} + H_2O \] Thus, chromate ions exist predominantly in a basic medium.