Question

Calculate the pH of a buffer solution containing 0.1 M CH₃COOH and 0.05 M CH₃COONa. Dissociation constant of CH₃COOH is 1.8 × 10^-5 at 25°C.

Answer 1

Given: [CH₃COOH] = 0.1 M,

[CH₃COONa] = 0.05 M; K_a = 1.8 × 10^-5; pH = ?

pK_a = - log₁₀ K_a

= -log10  1.8 × 10^-5

`= - (\bar5. 2553)`

`= \bar5 - 0.2553 = 4.7447`

`"pH" = "pK"_a + log_10 = ([CH_3COONa])/([CH_3COOH])`

`= 4.7447 + log_10  0.05/0.1`

`= 4.7447 + (\bar1. 6990)`

= 4.7447 + (- 1 + 0.6990)

= 4.7447 - 0.3010 = 4.4437

pH = 4.4437.