How many mL of 0.2 , M , KCN should be mixed | vedclass

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(D) The given solution is a buffer solution consisting of a weak acid $(HCN)$ and its salt $(KCN)$.Using the Henderson-Hasselbalch equation for an aci

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$0.1$

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(D) The given solution is a buffer solution consisting of a weak acid $(HCN)$ and its salt $(KCN)$.Using the Henderson-Hasselbalch equation for an acidic buffer:$pH = pK_a + \log \left( \frac{[Salt]}{[Acid]} ight)$Given: $pH = 3$,$pK_a = 6$,$[HCN] = 0.1 \, M$,$V_{HCN} = 200 \, mL$,$[KCN] = 0.2 \, M$.Let the volume of $KCN$ be $V \, mL$.$3 = 6 + \log \left( \frac{0.2 	imes V}{0.1 	imes 200} ight)$$-3 = \log \left( \frac{0.2V}{20} ight)$$-3 = \log \left( \frac{V}{100} ight)$$10^{-3} = \frac{V}{100}$$V = 100 	imes 10^{-3} = 0.1 \, mL$.

How many $mL$ of $0.2 \, M \, KCN$ should be mixed with $200 \, mL$ of $0.1 \, M \, HCN$ so as to make a mixture of $pH = 3$ ($pK_a$ for $HCN = 6$)?

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