Based on the data given below, which metal in its +2 oxidation state will not librate hydrogen from acids?

Co

The correct answer is Option (1) → Co

Step 1: Recall the principle

• Metals react with acids to liberate hydrogen if they are more electropositive than H⁺, i.e., if they can be oxidized by H⁺:

$M^{2+} + 2H^+ → M^{3+} + H_2$

• Compare standard potentials:
• H⁺/H₂ → 0 V
• Metal M²⁺/M³⁺: If $E^\circ > 0$, metal is less likely to be oxidized, i.e., will not liberate H₂.
• If $E^\circ < 0$, metal is more easily oxidized → reacts with acids → liberates H₂.

Step 2: Examine the given potentials

• Co: +1.97 → very positive → does not react with acids
• V, Ti, Cr → negative → will react → liberate H₂