NH 3 (aq) + H 2 O(l) NH 4 +(aq) + OH−(aq)
Second, write the equilibrium expression (use Kb(NH3)).
Kb(NH3) = Third, write the algebraic expression (plug in numbers
where you have them, and plug in letters where you
don’t).
(1.8 × 10−5) =
Since [NH 3 ] is at least 3 orders of magnitude larger
than Kb(NH3), we can now write
(1.8 × 10−5) =
Fourth, solve the algebraic expression.
(1.8 × 10−5) =
x^2 = (1.8 × 10−5) × (0.5 M) = 1 × 10−5