[Scyther_88]

Hello, I'm having a lot of trouble remembering how to do pH adjusting problems. Today was my first class of biochemsitry, and we got a some problem sets that involves pH adjusting. I looked online and even in my general chem. text book, but it wasn't much help. Can someone please walk me through this problem:

How many milliliters of 1M HCl are required to adjust 100 mL of 20 mM Na2HPO4 to pH 6.8?

Thanks for your time!

[Borek]

This is a buffer question, you add HCl to protonate HPO₄^2-.

[Scyther_88]

I understand that, but how do I start this problem?

[Borek]

Calculate necessary HPO₄^2-/H₂PO₄^- ratio using Henderson-Hasselbalch equation.