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 Cr2O72−⇌2CrO42−\mathrm{Cr_2O_7^{2-} \rightleftharpoons 2CrO_4^{2-}} is shifted to the right in:

Options
  1. a

    An acidic medium

  2. b

    A basic medium

    ✓
  3. c

    A neutral medium

  4. d

    A weakly acidic medium

Correct Answerb

A basic medium

Detailed Solution

Step 1 — Understand the equilibrium: Dichromate (Cr2O72−\mathrm{Cr_2O_7^{2-}}, orange) and chromate (CrO42−\mathrm{CrO_4^{2-}}, yellow) are interconverted depending on pH.

Step 2 — Effect of pH: The conversion involves H+\mathrm{H^+} ions: Cr2O72−+H2O⇌2CrO42−+2H+\mathrm{Cr_2O_7^{2-} + H_2O \rightleftharpoons 2CrO_4^{2-} + 2H^+}

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

Answer: Option (2) — Basic medium

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