Question

The pK_b of dimethylamine and pK_a of acetic acid are 3.27 and 4.77 respectively at T(K). The correct option for the pH of dimethylammonium acetate solution is ______.

Options

• 6.25

• 8.50

• 5.50

• 7.75

Answer 1

The pK_b of dimethylamine and pK_a of acetic acid are 3.27 and 4.77 respectively at T(K). The correct option for the pH of dimethylammonium acetate solution is 7.75.

Explanation:

Given:

pK_b of dimethylamine = 3.27

pK_a of acetic acid = 4.77

pH = `1/2` (pK_w + pK_a − pK_b)

Where pK_w = 14 at 298 K

∴ pH = `1/2 (14 + 4.77 - 3.27)`

= `1/2 (14 + 1.50)`

= `1/2 (15.50)`

pH = 7.75