What is the concentration of NH3 in 0.250M solution of NH4Cl?
..........NH4^+ H2O ==> NH3 + H3O^+
I.......0.250............0.....0
C.........-x.............x.....x
E.......0250-x...........x.....x
Ka for NH4^+ = (Kw/Kb for NH3) = (x)(x)/(0.250-x)
Solve for x = (NH3)