Chemistry

When you dilute a weak base, its ionization equilibrium shifts—the base ionizes more to partially offset the concentration drop. The key is recognizing that $K_b$ stays constant, so you need to recalculate the $[\text{OH}^-]$ at each concentration using the equilibrium expression, then convert both to $\text{pH}$ values. The difference tells you how much the $\text{pH}$ actually changes, which is always less than you'd predict from concentration alone.

When you dilute a weak base, its ionization equilibrium shifts—the base ionizes more to partially offset the concentration drop. The key is recognizing that $K_b$ stays constant, so you need to recalculate the $[\text{OH}^-]$ at each concentration using the equilibrium expression, then convert both to $\text{pH}$ values. The difference tells you how much the $\text{pH}$ actually changes, which is always less than you'd predict from concentration alone.