The pK_a of HCN is 9.30. What is the pH of a | vedclass

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(A) The given solution is a buffer solution consisting of a weak acid $(HCN)$ and its salt with a strong base $(KCN)$.We use the Henderson-Hasselbalch

Vedclass · Accepted Answer

$9$

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(A) The given solution is a buffer solution consisting of a weak acid $(HCN)$ and its salt with a strong base $(KCN)$.We use the Henderson-Hasselbalch equation for an acidic buffer:$pH = pK_a + \log \frac{[Salt]}{[Acid]}$Given:$pK_a = 9.30$$Moles \ of \ Salt \ (KCN) = 2.5 \ mol$$Moles \ of \ Acid \ (HCN) = 2.5 \ mol$Since the volume is the same for both,the ratio of concentrations is equal to the ratio of moles:$pH = 9.30 + \log \left( \frac{2.5}{2.5} \right)$$pH = 9.30 + \log(1)$Since $\log(1) = 0$,$pH = 9.30 + 0 = 9.30$

The $pK_a$ of $HCN$ is $9.30$. What is the $pH$ of a solution prepared by mixing $2.5 \ mol$ of $KCN$ and $2.5 \ mol$ of $HCN$ in $500 \ mL$ of water (in $.30$)?

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