If 1 mM solution of ethylamine produces pH =9, then the ionization constant ( K_b ) of ethylamine is 10^-x. The value of x is ____ (nearest integer).…

If $\displaystyle 1$ mM solution of ethylamine produces $\displaystyle \mathrm{pH}=9$, then the ionization constant $\displaystyle \left(\mathrm{K}_{\mathrm{b}}\right)$ of ethylamine is $\displaystyle 10^{-x}$. The value of $\displaystyle x$ is $\displaystyle \_\_\_\_$ (nearest integer). [The degree of ionization of ethylamine can be neglected with respect to unity.]