Calculate the hydroxide concentration of a solution that is 0.1 F with NH3, and

Question

0.25 F in respect to (NH4)2S04.

Answer 1

NH3 + H2O ==> NH4^+ + OH^-
and
(NH4)2SO4 ==> 2NH4^+ + SO4^2-
If [(NH4)2SO4] = 0.25 then [(NH4)^+] = 0.50

Use Kb = (NH4^+)(OH^-)/(NH3).
You know Kb, (NH4)^+ and (NH3). Solve for OH^-

You could use the Henderson-Hasselbalch equation, too, if you've had that in your course.