A student is asked to make an acetic acid/ acetate buffer with a pH of 4.10. The only materials on hand are 300 mL of white vinegar (5.00% by mass acetic acid, density = 1.006g/mL) and potassium acetate. How should the student proceed?

Answer 1

5% by mass means 5 g HAc/100 g soln.
5g = 5/60 mols = 0.0833.
volume = mass/density = 100/1.006 = 99.4 mL.
M = about 0.8M but you need to confirm that and do it more accurately than I.

pH = pKa + log (base)/(acid)
mols HAc = 0.300L x 0.8M = about 0.25
pKa = about 4.74 but use the value from your text.

4.10 = 4.74 + log (base)/(0.25)
Solve for mols base (this isn't the concn but is mols since you substituted mols for HAc.
Then convert mols KAc to grams. g = mols x molar mass.