Question

A buffer solution is prepared in which the concentration of NH₃ is 0.30 M and the concentration of \[\ce{NH^+_4}\] is 0.20 M. If the equilibrium constant, K_b tor NH₃ equals 1.8 × 10^-5, what is the pH of the solution?

Options

• 8.73

• 9.08

• 9.44

• 11.72

Answer 1

9.44

Explanation:

Given, K_b = 1.8 × 10^-5 

pK_b = - log K_b

= - log 1.8 × 10^-5 = 4.74

pOH = pK_b + log `(["salt"])/(["base"])`

`= 4.74 + log  0.20/0.30`

= 4.74 - 0.176

= 4.56

pH + pOH = 14

pH = 14 - 4.56 = 9.44