Question

Assertion: $H_2S$ is stronger acid than $PH_3$.
Reason: S is more electronegative than P, conjugate base $HS^-$ is more stable than $H_2P^-$.

• A. If both assertion and reason are true and reason is the correct explanation of assertion.
• B. If both assertion and reason are true but reason is not the correct explanation of assertion.
• C. If assertion is true but reason is false.
• D. If both assertion and reason are false.

Answer 1

Answer: (A)

$H_2S_{(g)} + aq \rightarrow HS^-_{(aq)} + H^+_{(aq)}$
$PH_{3(g)} + aq \rightarrow H_2^- + H^+_{(aq)}$
As S is more electronegative than P, conjugate base $HS_6^-$ is more stable than $H_2P^-$. Hence, $H_2S$ is stronger acid than $PH_3$.