Determine the ammonia concentration of an aqueous solution that has a pH of 11.30.The equation for the dissociation of NH₃ (K_b= 1.8 × 10^-5)is NH₃(aq)+ H₂O(l)⇌ NH₄⁺(aq)+ OH^-(aq).

Question

Quizplus · Accepted Answer

Ammonia (NH3) acts as a base in water and undergoes the following reaction:
NH3 + H2O ⇌ NH4+ + OH-
The equilibrium constant expression for this reaction is:
Kb = [NH4+][OH-]/[NH3]

pH = 11.30
pOH = 14 - pH = 2.70
[OH-] = 10^-pOH = 2.74 × 10^-3 M

Using the equilibrium constant expression and the pKb value, we can solve for [NH3]:
Kb = [NH4+][OH-]/[NH3]
1.8 × 10^-5 = (x)(2.74 × 10^-3)/x
x^2 = 5.23 × 10^-2
x = 0.228 M

Therefore, the ammonia concentration of the aqueous solution is 0.22 M (option B).

Determine the Ammonia Concentration of an Aqueous Solution That Has