HELP! Need to make 50mL of a buffer solution that has a pH of 9.7 in lab.. how do I do this?

Question

(Sorry for reposting but I haven't gotten one reply yet and I want to get this done as this week is gonna be nuts at school)

The concentration of any solute in the buffer solution can be no more than 1.0M

Need to know:

- the mass or volume of each reagent used.
- Glassware
- How the reagents are combined.
- The volume of the buffer solution to be prepared.

I can use various solutions and solids provided by the lab such as 6M HCl, 6M HNO3, 6M HC2H3O2, etc. and solids NaC2H3O2, NaHCO3, NH4Cl, Na2SO3 etc..

(Note: There is a big long list of things I can use.)

I don't know how to start approaching this. I need a procedure before I go into the lab.

Answer 1

I don't carry a table of Ka's with me, so I can't give you a definitive answer. It may help to convert pH to H+, which becomes 2x10-10. The reason for this is that you want to have an acid and its salt which have a Ka around that value. One candidate pair that strikes me is NaHCO3 and Na2CO3, or perhaps Na2HPO4 and Na3PO4. If the Ka is exactly 2x10-10, you can add equal moles of each to water to dissolve and add water to 1 liter (or whatever volume you want). If the Ka is somewhere around there, you can use the Ka expression to determine the ratio of moles of one to the other, and proceed as mentioned above.

Answer 2

Very easy...simply pee into a cup.