JEE Main · 2024 · Shift-IImediumDNF-044

The number of ions from the following that have the ability to liberate hydrogen from a dilute acid is ____. Ti2+,\,…

d & f-Block Elements · Class 12 · JEE Main Previous Year Question

Question

The number of ions from the following that have the ability to liberate hydrogen from a dilute acid is ____.

Ti2+,Cr2+\text{Ti}^{2+},\, \text{Cr}^{2+} and V2+\text{V}^{2+}

Options
  1. a

    2

  2. b

    3

  3. c

    1

  4. d

    0

Correct Answerb

3

Detailed Solution

Concept: Liberation of H₂ from dilute acid

An ion liberates H2\text{H}_2 from dilute acid if it is a strong enough reducing agent — i.e., it can reduce H+\text{H}^+ to H2\text{H}_2.

This requires the standard reduction potential E°Mn+/M(n1)+E°_{M^{n+}/M^{(n-1)+}} to be negative (or sufficiently low).

Checking each ion:

| Ion | M²⁺ Config | E° (V) | Liberates H₂? | |-----|------------|----------|----------------| | Ti2+\text{Ti}^{2+} | 3d23d^2 | 0.37-0.37 | Yes ✓ | | Cr2+\text{Cr}^{2+} | 3d43d^4 | 0.41-0.41 | Yes ✓ | | V2+\text{V}^{2+} | 3d33d^3 | 0.26-0.26 | Yes ✓ |

All three ions have negative reduction potentials and can act as reducing agents to liberate H2\text{H}_2 from dilute acids.

Answer: Option (2) — 3

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