What is the concentration of ammonia in a solution that is .500 M NH4Cl and in which the solubility of Mg(OH)2 is 1.0x10^-3 M? Ksp for Mg(OH)2 is 6.3x10^-10. Write the equilibrium equation and calculate the overall K.
NH3 + H2O ==> NH4^+ + OH^-
Kb = (NH4^+)(OH^-)/(NH3)
You know Kb and (NH4^+). (OH^-) comes from the solubility of Mg(OH)2 (that is OH^- will be twice the solubility of Mg(OH)2. (NH3) is the only unknown. Solve for that.