Answer is: pH of ammonium hydroxide is 11.13.
Chemical reaction of ammonium hydroxide in water: NH₄OH → NH₄⁺ +
OH⁻
.
Kb(NH₄OH) = 1,8·10⁻⁵.
c₀(NH₄OH) = 0.1 M.
c(NH₄⁺) = c(OH⁻) = x.
c(NH₄OH) = 0.1 M- x.
Kb = c(NH₄⁺) · c(OH⁻) / c(NH₄OH).
0,000018 = x² / 0.1 mol/L - x.
Solve quadratic equation: x = c(OH⁻) = 0.00133 M.
pOH = -logc(OH⁻).
pOH = 2.87.
pH = 14 - 2.87.
pH = 11.13.
