A student of biochemistry prepares a 0.125 mol dm-3 solution of a newly isolated monoprotic food preservative acid (HA\text{HA}HA) to test its antimicrobial efficacy. At 298 K, the student measures the pH of this solution to be 3.15.
What is the value of KaK_{\text{a}}Ka for this acid at 298 K, in mol dm−3\text{mol dm}^{-3}mol dm−3?
5.66×10−35.66 \times 10^{-3}5.66×10−3
4.01×10−64.01 \times 10^{-6}4.01×10−6
5.01×10−75.01 \times 10^{-7}5.01×10−7
6.26×10−86.26 \times 10^{-8}6.26×10−8
77 exam-style questions on AQA A Level Chemistry Acids and bases (A-level only), covering Brønsted–Lowry acid–base equilibria in aqueous solution (A-level only), Definition and determination of pH (A-level only), The ionic product of water, $K_w$ (A-level only), Weak acids and bases $K_a$ for weak acids (A-level only), pH curves, titrations and indicators (A-level only), and Buffer action (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.