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Assertion : $\mathrm{H}_3 \mathrm{BO}_3$ is a weak acid.
Reason: Water extracts the proton of $\mathrm{H}_3 \mathrm{BO}_3$.
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Reason: Water extracts the proton of $\mathrm{H}_3 \mathrm{BO}_3$.
Solution:
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Verified Answer
The correct answer is:
If assertion is true but reason is false.
$\mathrm{H}_3 \mathrm{BO}_3$ 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 $\mathrm{OH}^{-}$ion of $\mathrm{H}_2 \mathrm{O}$.
$\mathrm{H}-\mathrm{OH}+\mathrm{B}(\mathrm{OH})_3 \longrightarrow\left[\mathrm{B}(\mathrm{OH})_4\right]^{-}+\mathrm{H}^{+}$
$\mathrm{H}-\mathrm{OH}+\mathrm{B}(\mathrm{OH})_3 \longrightarrow\left[\mathrm{B}(\mathrm{OH})_4\right]^{-}+\mathrm{H}^{+}$
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