Question

Ammonia is a weak base. if the initial concentration of ammonia is 0.150 m and the equilibrium concentration of hydroxide is 0.0016m, calculate kb for ammonia.

Answer 1

Answer is: Kb for ammonia is 1.73·10⁻⁵.
Chemical reaction of ammonia in water: NH₃ + H₂O → NH₄⁺ + OH⁻.
Kb(NH₃) = ?.
c₀(NH₃) = 0.150 M.
c(NH₄⁺) = c(OH⁻) = 0.0016 M.
c(NH₃) = 0.150 M - 0.0016.
c(NH₃) = 0.1484 M.
Kb(NH₃) = c(NH₄⁺) · c(OH⁻) / c(NH₃).
Kb(NH₃) = (0.0016 M)² / 0.1484 M.
Kb(NH₃) = 1.73·10⁻⁵.