Question

Calculate the pH of a 0.033 M ammonia solution. If 0.033 M NH4Cl is introduced in this solution at the same temperature. (Kb for NH3 = 1.77 x 10-5)

Answer 1

To calculate the pH of the solution containing ammonia and NH4Cl, we will use the Handerson Hasselbach equation.

According to this equation,

pOH = pKb + log 

where, pKb is to be calculated from Kb.

Kb for NH3 = 1.7710-5

pKb = -log Kb = -log (1.7710-5) = 4.75

[Salt] = [NH4Cl] = 0.033 M

[Base] = [NH3] = 0.033 M

When we put all these values in the equation,

pOH = 4.75 + log 

= 4.75 + log (1) = 4.75+0 = 4.75

pOH = 4.75

pH = 14 - 4.75 = 9.25

pH = 9.25

pH of the solution = 9.25