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
