The pH of human blood needs to be between 7.35 and 7.45. You want to prepare a buffer

Question

solution that gives a pH of 7.40. You decide to use a sodium phosphate buffer: the acid is
H2PO−
4 and the conjugate base is HPO2−
4
. You want the concentration of the acid to be
0.0100 M.
1. If the initial H2PO−
4
concentration is 0.0100 M, what is the initial concentration of
HPO2−
4
that will give a pH of 7.40?
2. What is the maximum molarity of acid that this buffer can neutralize without the pH
dropping below 7.35?
3. What is the maximum molarity of base that this buffer can neutralize without the pH
going above 7.45?

I keep trying to post this question but i can;'t find it once i post it.. i was help with part one, but i cannot figure out part 2 and 3

Answer 1

You might help yourself if you used a name that isn't used often. Anonymous is used by several people so you can't tell which is your post.
I responded last night that I didn't think there was enough information to answer part 2 and part 3. You MUST hav a volume in that question somewhere. A simple M depends upon HOW MUCH of that M solution you have.

Answer 2

I have responded several times that I don't think it can be done without know the volume. I've changed my mind. I believe I know that they are asking for now. Here is what you do.
The problem you have for 2 gives you a 7.35 value. You know the base and acid for 7.40. Plug in 7.35 for the pH into the HH equation and the base you have, and calculate the M acid.

For 3 you use 7.45 and the acid you have and calculate the M of base you can add from the HH equation. Post you work if you get stuck.