Analytical Chemistry involving buffer

[jkh4]

1. The problem statement, all variables and given/known data

What volume of 0.200M HCl must be added to 250.0ml of 0.300M sodium mandelate to produce a buffer solution with a pH of 3.37?


2. Relevant equations
3. The attempt at a solution

For 2 and 3, can I use the equation pH = pKa + log [A-/HA]? but for HCl isn't that 100% disassociation? How can we use that if the Ka is not a given value for HCl?

Thanks.

[chemisttree]

You are correct... Think of the HCl being used only to protonate a portion of the sodium mandelate.

[Borek]

And assume this protonation is stoichiometric.

Borek
--
Stoichiometry calculator (http://www.chembuddy.com/?left=EBAS&right=equation-balancing-stoichiometry)
www.pH-meter.info/pH-electrode (http://www.ph-meter.info/pH-electrode)