Question

The composition of an acidic buffer mixture made up of HA and NaA of total molarity `0.29` having `pH=4.4` and `K_(a)=1.8xx10^(-5)` in terms of concentration of salt and acid respectively is:
A. `0.09M and 0.20M`
B. `0.20M and 0.09M`
C. `0.1M and 0.19M`
D. `0.19M and 0.10M`

Answer 1

Correct Answer - A
`pH= -log K_(a)+log ([Sal t])/([Acid])`
Let a mol `litre^(-1)` be concentration of salt, then concentration of acid `= (0.29-a)`
`4.4= -log 1.8xx10^(-5)+log(a)/((0.29-a))`
`:. A=0.09`
`[Sal t]= 0.09M`
`[Acid]= 0.29-0.09=0.20M`