Question

Assertion: $H_3BO_3$ is a weak acid.
Reason: Water extracts the proton of $H_3BO_3$.

• 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: (C)

$H _3 BO _3$ is a very weak monobasic acid $\left( K _{ a }=5.6 \times 10^{-10}\right)$ but it does not act as a proton donor. It behaves as a Lewis acid i.e., it accepts a pair of electrons from $OH ^{-}$ion of $H _2 O$.
$H - OH + B ( OH )_3 \longrightarrow\left[ B ( OH )_4\right]^{-}+ H ^{+}$