Lawrie Ryan and Roger Norris Solutions for Chapter: Further Aspects of Equilibria, Exercise 18: EXAM-STYLE QUESTIONS

Calculate the pH of $0.004 00 \mathrm{mol} {\mathrm{dm}}^{-3}$ butanoic acid(aq). $\left({\mathrm{K}}_{\mathrm{a}} = 1.51 \mathrm{x} {10}^{-5} \mathrm{mol} {\mathrm{dm}}^{-3}\right)$

$0.25 \mathrm{mol}$ of sodium hydroxide is dissolved in $2.00 {\mathrm{dm}}^3$ of water. Calculate the concentration and pH of the sodium hydroxide solution.$\left({\mathrm{K}}_{\mathrm{w}} = 1.00 \mathrm{x} {10}^{-14} \mathrm{mol} {\mathrm{dm}}^{-3}\right)$

Calculate the $\mathrm{pH}$ of a solution containing $0.100 \mathrm{mol} {\mathrm{dm}}^{-3}$ ethanoic acid and $0.100 \mathrm{mol} {\mathrm{dm}}^{-3}$ sodium ethanoate? $\left({\mathrm{K}}_{\mathrm{a}} \mathrm{of} {\mathrm{CH}}_3\mathrm{COOH}= 1.74 \mathrm{x} {10}^{-5} \mathrm{mol} {\mathrm{dm}}^{-3}\right)$

How many moles of sodium ethanoate must be added $2.00 {\mathrm{dm}}^3$ of $0.0100 \mathrm{mol} {\mathrm{dm}}^{-3}$ ethanoic acid to produce a buffer solution $\mathrm{pH} 5.40$? $\left({\mathrm{K}}_{\mathrm{a} }\mathrm{of} \mathrm{ethanoic} \mathrm{acid} =1.74\times {10}^{-5 }\mathrm{mol} {\mathrm{dm}}^{-3}\right)$

Explain why the $\mathrm{pH}$ of a solution containing $0.100 \mathrm{mol} {\mathrm{dm}}^{-3}$ ethanoic acid and $0.100 \mathrm{mol} {\mathrm{dm}}^{-3}$ sodium ethanoate does not change significantly when a small amount of hydrochloric acid is added.

Deduce the pH of $0.25 \mathrm{mol} {\mathrm{dm}}^{-3} \mathrm{HCl}\left(\mathrm{aq}\right)$.

Deduce the pH of $0.0500 \mathrm{mol} {\mathrm{dm}}^{-3}$ sodium hydroxide.$\left({\mathrm{K}}_{\mathrm{w}} = 1.00 \mathrm{x} {10}^{-14} \mathrm{mol} {\mathrm{dm}}^{-3}\right)$

Propanoic acid is a weak acid. A $0.0500 \mathrm{mol} {\mathrm{dm}}^{-3}$ solution of propanoic acid has a $\mathrm{pH}$ of $3.1$ . Calculate the value of ${\mathrm{K}}_{\mathrm{a}}$, for propanoic acid. Show all your working.