JEE Main · 2024 · Shift-IIeasyCEQ-011

The equilibrium Cr2O72- 2CrO42- is shifted to the right in:

Chemical Equilibrium · Class 11 · JEE Main Previous Year Question

Question

The equilibrium $\mathrm{Cr_2O_7^{2-} \rightleftharpoons 2CrO_4^{2-}}$ is shifted to the right in:

Options

a
An acidic medium
b
A basic medium
✓
c
A neutral medium
d
A weakly acidic medium

Correct Answerb

A basic medium

Detailed Solution

Step 1 — Understand the equilibrium: Dichromate ( $\mathrm{Cr_2O_7^{2-}}$ , orange) and chromate ( $\mathrm{CrO_4^{2-}}$ , yellow) are interconverted depending on pH.

Step 2 — Effect of pH: The conversion involves $\mathrm{H^+}$ ions: $\mathrm{Cr_2O_7^{2-} + H_2O \rightleftharpoons 2CrO_4^{2-} + 2H^+}$

In acidic medium (high $[\mathrm{H^+}]$ ): Equilibrium shifts left (toward dichromate)
In basic medium (low $[\mathrm{H^+}]$ , high $[\mathrm{OH^-}]$ ): $\mathrm{OH^-}$ neutralizes $\mathrm{H^+} \rightarrow$ equilibrium shifts right (toward chromate) ✓

Answer: Option (2) — Basic medium

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