Define the term conjugate acid-base pair.
The $pK_a$ of $\text{HCOOH}$ is 3.75 and that of $\text{CH}_3\text{CH}_2\text{COOH}$ is 4.87. Complete the Brønsted-Lowry equilibrium for the stronger acid reacting with water: $\dots + \text{H}_2\text{O} \rightleftharpoons \dots + \dots$
Write the expression for the acid dissociation constant, $K_a$, of butanoic acid, $\text{CH}_3\text{CH}_2\text{CH}_2\text{COOH}$.
The $pK_a$ of $\text{CH}_3\text{CH}_2\text{CH}_2\text{COOH}$ is 4.82. A solution of $\text{CH}_3\text{CH}_2\text{CH}_2\text{COOH(aq)}$ has pH 3.25. Calculate the concentration, in $\text{mol dm}^{-3}$, of $\text{CH}_3\text{CH}_2\text{CH}_2\text{COOH}$ in this solution.
Define the term buffer solution.
A buffer solution containing a mixture of $\text{CH}_3\text{COOH}$ and $\text{CH}_3\text{COONa}$ is prepared as follows. $600\,\text{cm}^3$ of $\text{CH}_3\text{COOH}$ solution is blended with $400\,\text{cm}^3$ of $0.125\,\text{mol dm}^{-3}$ $\text{CH}_3\text{COONa}$. The buffer solution has pH 5.70. The $K_a$ of $\text{CH}_3\text{COOH}$ is $1.78 \times 10^{-5}\,\text{mol dm}^{-3}$. Calculate the initial concentration, in $\text{mol dm}^{-3}$, of $\text{CH}_3\text{COOH}$ used.
A fuel cell is an electrochemical cell that generates electrical energy by using oxygen to oxidise a fuel. Methanoic acid, $\text{HCOOH}$, is being studied as a fuel in fuel cells. When the cell runs, $\text{HCOOH}$ is oxidised to carbon dioxide. The half-equation at the cathode is: $\text{O}_2 + 4\text{H}^+ + 4e^- \rightarrow 2\text{H}_2\text{O}$. In this fuel cell, the overall cell reaction is identical to that for the complete combustion of $\text{HCOOH}$. Deduce the half-equation for the reaction at the anode.
Calculate the volume, in $\text{cm}^3$, of oxygen consumed when the cell delivers a current of $3.75\,\text{A}$ for $40.0\,\text{minutes}$. Assume room conditions.