Question

You have 250mL of a 0.56M solution of sodium acetate. How many mL of 0.50M acetic acid should be added to make a buffer of pH 4.40?

I think this is a buffer system so I would use pH=pka + log base/acid

so would I set this up as
4.40 = 4.74 + log base/ 1.8e-5 from acetic acid?

Answer 1

Yes and no. (acid) is not 1.8E-5; that's ka for acetic acid. You put 250*0.56 for base and mL*0.500 for acid; solve for mL acid.