Answer is: pH of ammonia solution is 11,43.
Chemical reaction of ammonia in water: NH₃ + H₂O → NH₄⁺ + OH⁻.
Kb(NH₃) = 1,8·10⁻⁵.
c₀(NH₃) = 0,44 M = 0,44 mol/L.
c(NH₄⁺) = c(OH⁻) = x.
c(NH₃) = 0,44 mol/L - x.
Kb = c(NH₄⁺) · c(OH⁻) / c(NH₃).
0,000018 = x² / (0,4 mol/L - x).
x² + 0,000018x
- 0,0000072 = 0.
solve quadratic equation: x
= c(OH⁻) =
2,67·10⁻³ mol/L.
pOH = -log(2,67·10⁻³ mol/L) = 2,57.
pH = 14 - 2,57 = 11,43.
