[kylon]

How to prepare a buffer solution of pH 4.8 from C₆H₅COOH and C₆H₅COONa at 0.20M??

[sdekivit]

determine the acid - conjugated base ratio using the hendersson-hasselbalch equation at pH = 4.8

you also know the concentration must be 0.20 M --> you now have two equation with 2 unknowns.

[kylon]

Sorry I miss some important infomations.
1. C₆H₅COOH has a Ka of 6.46*10^-5
2. 0.10 M C₆H₅COOH and 0.25 M C₆H₅COONa are used.

then axplain how to prepare the buffer solution...

[Borek]

It is not possible to prepare buffer as described.

[kylon]

To make the question more detailly and clear, I show whole question for you all.

Benzoic acid, C₆H₅COOH has a K_a of 6.46*10^-5.

a) calculate the pH of a buffer solution consisting of 0.10M C6H5COOH and 0.25M C6H5COONa.

b) explain how to prepare a buffer solution of pH 4.8 form C6H5COOH and C6H5COONa at 0.20M.

I think it will help you and me to solve this question. Thank!

[AWK]

a - just use Henderson-Haselbach equation
b -Think what does mean 0.20 M buffer. Hint - when you mix solution the concetration of reagents changes (and eventually you should use some water).