Calculate the ratio of $\mathrm{pH}$ of a solution containing $1 \mathrm{~mol}$ of $\mathrm{NaCN}+1…
Calculate the ratio of $\mathrm{pH}$ of a solution containing $1 \mathrm{~mol}$ of $\mathrm{NaCN}+1 \mathrm{~mol}$ of $\mathrm{HNO}_{3}$ per liter and of other solution containing lmol NaCN + lmol of HCN per litre
Given $: \mathrm{K}_{\mathrm{a}}$ of $\mathrm{HCN}$ is the order of $10^{-10}$.
$1: 1$
$2: 1$
$1: 2$
Data insufficient
Solution
$K_{a}$ of $H C N$ is the order of $10^{-10}$ so at this concentration, a of HCN will be negligible.
\(\begin{array}{cccc}
\mathrm{NaCN} & + & \mathrm{HNO}_3 & ightarrow & \mathrm{HCN} & + & \mathrm{NaNO}_3 \\
1 & & 1 & & \\
0 & & 0 & & 1 & & 1
\end{array}\)
$[\mathrm{HCN}]=1 \mathrm{M}$
$\mathrm{pH}_{1}=\frac{1}{2} \mathrm{pK}_{\mathrm{a}}-\frac{1}{2} \log 1$
$\mathbf{p H}_{\mathbf{2}}=\mathbf{p} \mathbf{K}_{\mathbf{a}}$
$\frac{\mathrm{pH}_{1}}{\mathrm{p} \mathrm{H}_{2}}=\frac{1}{2}$