Analytical Chemistry involving buffer

[jkh4]

Homework Statement

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?

Homework Equations

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.