Answer:
4.74.
Step-by-step explanation:
The equilibrium equation for the hydrolysis of NH4+ is:
NH4+ + H2O ⇌ NH4OH + H+
The Cl- ion is a strong base and will not undergo hydrolysis in water. Therefore, the Cl- ion will not affect the pH of the solution.
Use the equilibrium constant for the hydrolysis of NH4+ (Kb) to calculate the pH of the solution.
The expression for the equilibrium constant for the hydrolysis of NH4+ is:
Kb = [NH4OH][H+] / [NH4+]
Given that the concentration of NH4Cl is 1.0 mol/L, the concentration of NH4+ ions is also 1.0 mol/L.
The concentration of hydroxide ions (OH-) can be calculated from the Kb expression:
Kb = [NH4OH][H+] / [NH4+]
[OH-] = Kb * [NH4+]
Knowing that the Kb for NH4+ = 1.810^-5
[OH-] = 1.810^-5 * 1.0 = 1.8*10^-5 M
The pH of the solution is the negative logarithm of the hydroxide ion concentration:
pH = -log([OH-])
pH = -log(1.8*10^-5)
pH = 4.74
Therefore, the pH of 1.0 mol/L solution of NH4Cl is 4.74.