The ion product of water (Kw) is the product of the acid dissociation constant (Ka) and the base dissociation constant (Kb) : Ka×Kb=Kw So, you can solve for Kb using: Kb=‌
Kw
Ka
We know: ‌Kw=1.0×10−14‌ at ‌25∘C ‌Ka=1.8×10−4 Plug these values into the formula: ‌Kb=‌