Chapter 16 Principles of Chemical Reactivity: The Chemistry of Acids and Bases - Study Questions - Page 629c: 48

See the answer below.

a) $[H_3O^+]=10^{-pH}=8.13\cdot10^{-11}\ M$ $[OH^-]=K_w/[H_3O^+]=1.23\cdot10^{-4}\ M$ b) Assuming one mol of hydroxide per mol of the base(AOH), $[A]= 1.23\cdot10^{-4}\ M$, $K_b=(1.23\cdot10^{-4})^2/(0.015-1.23\cdot10^{-4})=1.017\cdot10^{-6}$ It is a moderately weak base.