How to prepare buffer solutions? - I need some help here! (Nov/18/2008 )

"I am asked to make 250.0 mL buffer with pH = 7.00. I am only given a stock solution of 0.2000 mol/L H3PO4 and a stock solution of 0.2000 NaOH. Unfortunately the distilled water supply is temporarily unavailable so I can only use the H3PO4 and NaOH solutions. What are the volumes of H3PO4 and NaOH solutions, respectively, that I will need to take to make the requested buffer solution? "

Please help!

Thanks!

What is the final concentration of the buffer?

That's the problem, it is not given...

First step: Ask...what type of buffer? and final concentration?
Second step: Read the recipe of the buffer if don't have one look in the Protocols books like Maniatis or Short Protocols, etc.
Third step: Before begin the mixing check that you have all the ingredients including the water and that anything is contaminated.
fourth Mix the ingredients according to recipe.

This looks silly, but as a lab. tec that have seen many students that don't follow instructions...
Always Ask, the only stupid question is the one don't asked