The pK_b of CN^{Theta} is 4.7. The pH of a so | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(B) The mixture of a weak acid $(HCN)$ and its salt with a strong base $(KCN)$ forms an acidic buffer solution.For an acidic buffer,the $pH$ is given

Vedclass · Accepted Answer

$9.3$

Vedclass · Answer

(B) The mixture of a weak acid $(HCN)$ and its salt with a strong base $(KCN)$ forms an acidic buffer solution.For an acidic buffer,the $pH$ is given by the Henderson-Hasselbalch equation:$pH = pK_a + \log \left(\frac{[Salt]}{[Acid]}\right)$Given $pK_b$ of $CN^{\Theta} = 4.7$,we calculate $pK_a$ of $HCN$:$pK_a = 14 - pK_b = 14 - 4.7 = 9.3$Since the number of moles of salt $(KCN)$ and acid $(HCN)$ are equal ($2.5 \ mol$ each),the ratio $\frac{[Salt]}{[Acid]} = 1$.Therefore,$pH = 9.3 + \log(1) = 9.3 + 0 = 9.3$.

The $pK_b$ of $CN^{\Theta}$ is $4.7$. The $pH$ of a solution prepared by mixing $2.5 \ mol$ of $KCN$ and $2.5 \ mol$ of $HCN$ in water and making the total volume up to $500 \ mL$ is:

Similar Questions

$A$ physician wishes to prepare a buffer solution at $pH = 3.58$ that efficiently resists changes in $pH$ yet contains only small concentration of the buffering agents. Which of the following weak acids together with its sodium salt would be best to use?

$20 \ mL$ solution contains $0.1 \ M \ NH_4Cl$ and $0.01 \ M \ NH_4OH$. By adding which one will its $pH$ not change?

Which one of the following pairs of solutions is not an acidic buffer?

In which of the following does a buffer solution play an important role?

Which of the following solutions does not act as a buffer $:-$

Vedclass Test Series

Exam Paper Generator

Online Exam Module