[garfield6369]

Calculate the volume of 1.00 M acetic acid solution and mass of sodium acetate needed to make 250 mL of a 0.450 M acetic acid/acetate buffer solution with a pH of 4.00. (The pKa is 4.74 for acetic acid)

[Babcock_Hall]

According to forum rules, you must show an attempt before we can help you.  I'll give you a hint, though.  I would probably start this problem by calculating the ratio of acetic acid to acetate first (others might have a better idea).