Which buffer solution has maximum pH?

Options

A. mixture which is 0.1 M in `CH_3 COOH and 0.1 M is CH_3 COONa [pK_a (CH_3COOH )= 4.74`
B. mixture which is `0.2 M CH_3 COOH and 0.2 M is CH_3 COONa`
C. mixture which is `0.1 M ` in ` NH_4 Cl and 0.1 M `in `NH_4 OH [pK_a (NH_4^(+)) =9.26]`
D. all the solution have equal pH which is `4.74`

Answer

C

Explanation

( a ) ` pH =pKa +log ""(0.1)/(0.1) =4.74`
( b ) ` pH =pKa +log ""(0.2)/(0.2) =4.74`
( c ) ` pH =pKa +log ""(0.1)/(0.1) =9.26`