The equilibrium equations and `K_(a)` values for three acids are given at `25^(@)C:`
`HA(aq)" "+" "H_(2)OhArrH_(3)O^(+)(aq)" "+" "A^(-)(aq),K_(a)=2xx10^(-5)`
`HB(aq)" "+" "H_(2)OhArrH_(3)O^(+)(aq)" "+" "B^(-)(aq),K_(a)=4xx10^(-6)`
`HC(aq)" "+" "H_(2)OhArrH_(3)O^(+)(aq)" "+" "C^(-)(aq),K_(a)=1xx10^(-4)`
Which conjugate pair would be best for preparing a buffer with a `pH=5.4?(log2=0.3)`

Options

A. `HA+A^(-)`
B. `HB+B^(-)`
C. `HC+C^(-)`
D. `H_(2)O+H_(3)O^(+)`

Answer

B

Explanation

`5-log2
`6-log4" "6-0.6=5.4" "HB+B^(-)`
|Ph-Pk_(a)|to" Lesser this different, better will be the buffer"`