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Assertion (A) The $\mathrm{pH}$ of a buffer solution containing equal moles of acetic acid and sodium acetate is 4.8 ( $\mathrm{p} K_a$ of acetic acid is 4.8).
Reason (R) The ionic product of water at $25^{\circ} \mathrm{C}$ is $10^{-14} \mathrm{~mol}^2 . \mathrm{L}^{-2}$. The correct answer is
Options:
Reason (R) The ionic product of water at $25^{\circ} \mathrm{C}$ is $10^{-14} \mathrm{~mol}^2 . \mathrm{L}^{-2}$. The correct answer is
Solution:
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Verified Answer
The correct answer is:
Both (A) and (R) are true and (R) is not the correct explanation of (A)
Both (A) and (R) are true statement but (R) is not the correct explanation of (A). $\mathrm{pH}$ of a buffer solution is given by Henderson-Haselbalch equation.
$\begin{aligned}
& \mathrm{pH}=\mathrm{p} K_a+\log \frac{[\text { salt }]}{\text { [acid }]} \\
& \therefore \quad \mathrm{pH}=\mathrm{p} K_a(\text { when }[\text { salt }]=[\text { acid }]) \\
&
\end{aligned}$
$\begin{aligned}
& \mathrm{pH}=\mathrm{p} K_a+\log \frac{[\text { salt }]}{\text { [acid }]} \\
& \therefore \quad \mathrm{pH}=\mathrm{p} K_a(\text { when }[\text { salt }]=[\text { acid }]) \\
&
\end{aligned}$
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