Sergey Bylikin, Gary Horner and, Brian Murphy Solutions for Chapter: Acids and Bases (AHL), Exercise 2: Questions

Distinguish between the terms strong and weak acid and state the equations used to show the dissociation of acids ${\mathrm{HNO}}_3$ and $\mathrm{HCN}$ in aqueous solution.

Ammonia can be converted into nitric acid, ${\mathrm{HNO}}_3\left(\mathrm{aq}\right)$, and hydrocyanic acid, $\mathrm{HCN}\left(\mathrm{aq}\right)$. The ${\mathrm{pK}}_{\mathrm{a}}$ of hydrocyanic acid is $9.21$.

Deduce the expression for the ionization constant, ${\mathrm{K}}_{\mathrm{a}}$, of hydrocyanic acid and calculate its value from the ${\mathrm{pK}}_{\mathrm{a}}$ value given.

Ammonia can be converted into nitric acid, ${\mathrm{HNO}}_3\left(\mathrm{aq}\right)$, and hydrocyanic acid, $\mathrm{HCN}\left(\mathrm{aq}\right)$. The ${\mathrm{pK}}_{\mathrm{a}}$ of hydrocyanic acid is $9.21$.

Calculate the $\left[{\mathrm{H}}^{+}\right]$ and the $\mathrm{pH}$ of an aqueous solution of hydrocyanic acid of concentration $0.108 \mathrm{mol} {\mathrm{dm}}^{-3}$. State one assumption made in arriving at your answer.

$0.100 \mathrm{mol}$ of ammonia, ${\mathrm{NH}}_3$, was dissolved in water to make $1.00 {\mathrm{dm}}^3$ of solution. This solution has a hydroxide ion concentration of $1.28\times {10}^{-3} \mathrm{mol} {\mathrm{dm}}^{-3}$. Determine the $\mathrm{pH}$ of the solution.

$0.100 \mathrm{mol}$ of ammonia, ${\mathrm{NH}}_3$, was dissolved in water to make $1.00 {\mathrm{dm}}^3$ of solution. This solution has a hydroxide ion concentration of $1.28\times {10}^{-3} \mathrm{mol} {\mathrm{dm}}^{-3}$. Calculate the base dissociation constant, ${\mathrm{K}}_{\mathrm{b}}$, for ammonia.

Consider an acid–base indicator solution.

$$\begin{gathered} \mathrm{HIn}\left(\mathrm{aq}\right) \rightleftharpoons {\mathrm{H}}^{+}\left(\mathrm{aq}\right)+{\mathrm{In}}^{-}\left(\mathrm{aq}\right) \\ \mathrm{colour} \mathrm{A} \mathrm{colour} \mathrm{B} \end{gathered}$$

What is the effect on this acid–base indicator when sodium hydroxide solution is added to it?

Which indicator would be the most appropriate for titrating aqueous ethylamine, ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{NH}}_2$ , with nitric acid, ${\mathrm{HNO}}_3$?

The graph below shows the titration curve of $25{\mathrm{cm}}^3$ of $0.100 \mathrm{mol} {\mathrm{dm}}^{-3}$ of hydrochloric acid with sodium hydroxide, of $0.100 \mathrm{mol} {\mathrm{dm}}^{-3}$concentration. The indicator methyl orange was used to determine the equivalence point. Methyl orange has a pH range of $3.1–4.4$.

If the hydrochloric acid was replaced by ethanoic acid of the same volume and concentration, which property of the titration would remain the same?