Chapter 8, Problem 73E

A student dissolves $\text{0}\text{.0100 mole}$ of an unknown weak base in $\text{100}\text{.0 mL}$ water and titrates the solution with $0.100M{\text{ HNO}}_3.$ After $\text{40}\text{.0 mL of 0}\text{.100 }M{\text{ HNO}}_3$ was added, the $\text{pH}$ of the resulting solution was $\mathrm{8.00.}$ Calculate the $K_{\text{b}}$ value for the weak base.