A buffer solution contains 0.1 mole of sodium acetate dissolved in `1000 cm^(3)` of 0.1 M acetic acid. To the above buffer solution, 0.1 mole of sodium acetate is further added and dissolved. The pH of the resulting buffer is

Options

A. `pK_(a)`
B. `pK_(a)+2`
C. `pK_(a)-log2`
D. `pK_(a)+log2`

Answer

D

Explanation

Number of moles of acetic acid =0.1 mole
Total number of moles of sodium acetate present in buffer solution =-0.1+0.1=0.2 mole
`therefore pH=pK_(a)+log([CH_(3)COONA])/([CH_(3)COOH])`
`=pK_(a)+log(0.2)/(0.1)=pK_(a)+log2`
`thereforepH=pK_(0)+log2`