Give mathematical expressions for the following terms: pH; $K_a$ for a weak acid, $\text{HA}$.
Write equations to show how a buffer made from a mixture of $\text{HA}(aq)$ and $\text{NaA}(aq)$ resists pH change when an acid or an alkali is introduced.
When chlorine dissolves in water, this reaction occurs: $$\text{Cl}_2(g) + \text{H}_2\text{O}(l) \rightarrow \text{HClO}(aq) + \text{H}^+(aq) + \text{Cl}^-(aq)$$ Chlorine is dissolved in water to make $1000\ \text{cm}^3$ of a solution containing $0.170\ \text{mol}$ of $\text{HClO}$ and $0.170\ \text{mol}$ of $\text{HCl}$. A buffer solution is then made by adding $0.200\ \text{mol}$ of $\text{NaOH}(s)$ to this solution. The NaOH reacts first with the HCl. Calculate the pH of the buffer solution. [$\text{HClO}$ is a weak acid with $K_a = 2.9 \times 10^{-8}\ \text{mol dm}^{-3}$.]