Determine the ammonia concentration of an aqueous solution that has a pH of 11.50.The equation for the dissociation of NH₃ (K_b = 1.8 × 10^-5)is NH₃(aq)+ H₂O(l)⇌ NH₄⁺(aq)+ OH^-(aq). A)2.5 M B)0.55 M C)5.7 × 10^-3 M D)3.2 × 10^-3 M

Question

Quizplus · Accepted Answer

The dissociation of ammonia in water is given by the following equation:

NH3 + H2O ⇌ NH4+ + OH-

The equilibrium constant for this equation, known as the base dissociation constant (Kb), is given by:

Kb = [NH4+][OH-]/[NH3]

Since pH + pOH = 14 and pOH can be calculated from the given pH, we can solve for [OH-]:

pOH = 14 - pH = 2.50
[OH-] = 10^-pOH = 3.16 × 10^-3 M

Using the equation for Kb and the value of [OH-], we can solve for [NH3]:

Kb = [NH4+][OH-]/[NH3]
1.8 × 10^-5 = x^2 / (0.050 - x)

Solving for x gives:

x = [NH3] = 0.55 M

Therefore, the answer is B).

Determine the Ammonia Concentration of an Aqueous Solution That Has