Question

Metals which liberate hydrogen on treatment with acids must be:

• A. more electronegative than hydrogen
• B. less electropositive than hydrogen
• C. more electropositive than hydrogen
• D. higher compound

Answer 1

Answer: (C)

Let us consider a general reaction of a metal with an acid.

$2M+2HA⟶2MA+H_2\uparrow$

To displace $A^{-}$ ion from $HA$, the metal $M$ should be more electropositive than $H^{+}$ so that it can form more stable oxide. If the metal is less electropositive, it would not be able to displace $A^{-}$ ion from $HA$ because the $H-A$ bond will be strong due to more difference between the electronegativity of $H$ and $A$.

Thus the answer is option (D) more electropositive than hydrogen.