JEE Main · 2019 · Shift-IeasyDNF-027

The metal that gives hydrogen gas upon treatment with both the acid as well as the base is:

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

Question

The metal that gives hydrogen gas upon treatment with both the acid as well as the base is:

Options
  1. a

    Zinc

  2. b

    Magnesium

  3. c

    Iron

  4. d

    Mercury

Correct Answera

Zinc

Detailed Solution

Amphoteric metals react with both acids and bases to liberate H2\text{H}_2.

Zinc with acid: Zn+H2SO4ZnSO4+H2\text{Zn} + \text{H}_2\text{SO}_4 \rightarrow \text{ZnSO}_4 + \text{H}_2\uparrow

Zinc with base: Zn+2NaOHNa2ZnO2+H2\text{Zn} + 2\text{NaOH} \rightarrow \text{Na}_2\text{ZnO}_2 + \text{H}_2\uparrow

Why others fail:

  • Mg: reacts with acid but not with NaOH (not amphoteric)
  • Fe: reacts with dilute acid but not with NaOH
  • Hg: does not react with dilute acids or bases

Zn is amphoteric — its oxide (ZnO) and hydroxide Zn(OH)2\text{Zn(OH)}_2 are also amphoteric.

Answer: Option (1) — Zinc

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