Buffer Creation - Specifically acetate buffers (Apr/13/2009 )

For a project, I am supposed to create a .5 M acetate buffer with a pH of 3.5 using only sodium acetate (NaCH₃COO) and acetic acid (CH₃COOH).

Would it be correct to use the equation
HAc + Ac^- + 2H₂O <-> Ac^- + 2H₃O⁺ + 2OH^- + HAc
(With Ac being acetate)

Also, I calculated that 2.44 M HAc is needed. Is that correct?

Thanks in advance.

the easiest way to do this is to prepare 0.5M HAc and 0.5M NaAc and mix them until you reach your desired pH (there are tables available that will tell you the ideal proportions, this gives a starting point from which you can adjust the solution, or you can just take one and add the other until you reach the desired pH).