NH3 + H20--> NH4+ + OH-?
Ammonia is a weak base that dissociated in water, as shown above. At 25°C, the base dissociation constant, Kb, for NH3 is 1.8 x 10-5.
a. Determine the hydroxide ion concentration and the percentage dissociation of a 0.150 molar solution of ammonia.
b. Determine the pH of a solution prepared by adding 0.0500 mole solid ammonium chloride to 100. milliliters of 0.150 molar solution of ammonia.
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1.8 x 10^-5 = x^2 / 0.150 -x
x = [OH-] =0.00164 M
% = 0.00164 x 100 / 0.150 = 1.10
[NH4+] = 0.0500 mol / 0.100 L = 0.500
pKb = 4.7
pOH = 4.7 + log 0.500 / 0.150 = 5.2
pH = 14 - 5.2 =8.8
NH3 accepted a proton (which is H+ --- a hydrogen atom missing its electron = a proton) from H2O, giving you NH4+ and OH-.