The pH of a buffer solution prepared by adding 20 mL of 0.2 M `CH_(3)COOH` and 20 mL of 0.1 M sodium acetate will be : (given `pK_(a)` for `CH_(3)COOH = 4.74`)

Options

A. `4.43`
B. 3.04
C. 5.04
D. 3.05

Answer

C

Explanation

Number of moles of `CH_(3)COOH = (MV)/(1000) = (0.1 xx 10)/(1000) = 0.001`
Number of moles of `CH_(3)COONa = (MV)/(1000) = (0.1 xx 20)/(1000) = 0.02`
`pH = pK_(a) + log""(["Salt"])/(["Acid"]) = 4.74 + log [(0.002)/(0.001)] = 5.04`