Question

A buffer solution contains 100mL of 0.01 M `CH_(3)COOH` and 200mL of 0.02 M `CH_(3)COONa`. 700mL of water is added, pH before and after dilution are `(pK_(a)=4.74)`
A. 5.04,5.04
B. 5.04,0.504
C. 5.04,1.54
D. 5.34,5.34

Answer 1

Correct Answer - D
In mixture (before dilution )
`[CH_(3)COOH]=(0.01 xx 100)/(300)=(0.01)/(3)M`
`[CH_(3)COONa]=(0.02 xx 200)/(300)=(0.04)/(3)M`
`pH =pK_(a)+log. (["salt"])/(["acid"])`
`=4.74 +log.(004)/(3) xx (3)/(0.01)`
`=4.74 +log4`
`=4.74 +0.60 =5.34`
On dilution , no change in pH will take place.