Problem: If Kb for NX3 is 4.5×10−6, what is the percent ionization of a 0.325 M aqueous solution of NX3?Express your answer numerically to three significant figures.

We are being asked to calculate the percent ionization of a 0.325 M aqueous solution of NX₃. 

Recall that the percent ionization is given by:

$\boxed{\mathbf{\%}\mathbf{ }\mathbf{ionization}\mathbf{=}\frac{\mathbf{\left[}{\mathbf{OH}}^{\mathbf{-}}\mathbf{\right]}}{\mathbf{[}\mathbf{B}{\mathbf{]}}_{\mathbf{initial}}}\mathbf{\times }\mathbf{100}}$

We know the initial concentration of NX₃, 0.325 M. We just need to find the concentration of OH^- at equilibrium.

NX₃ has a low K_b, therefore we know that it is a weak base.

Since we’re dealing with a weak base and K_b is an equilibrium expression, we will have to create an ICE chart to determine the equilibrium concentration of each species:

• NX₃ → weak base → proton acceptor
• H₂O → will act as the weak acid → proton donor

Equilibrium reaction:       NX_3(aq) + H₂O_(l) ⇌ NX₃H⁺_(aq) + OH^-_(aq)