Chapter 7, Problem 86E

Quinine ${\text{(C}}_{\text{20}}{\text{H}}_{\text{24}}{\text{N}}_{\text{2}}{\text{O}}_{\text{2}}\text{)}$ is the most important alkaloidderived from cinchona bark. It is used as an antimalarialdrug. For quinine $\text{p}{K}_{\text{b}}{}_{{}_1}=5.1\text{ and p}{K}_{\text{b}}{}_{{}_2}=9.7(\text{p}{K}_{\text{b}}=-\log K_{\text{b}})$ . Only 1.0 g of quinine will dissolve in1900.0 mL of solution. Calculate the pH of a saturatedaqueous solution of quinine. Consider only the reaction ${\text{Q+H}}_{\text{2}}\text{O}\rightleftharpoons {\text{QH}}^{\text{+}}{\text{+OH}}^{\text{–}}$ described by $\text{p}{K}_{{\text{b}}_1}$ , where $\text{Q=quinine}$ .