[AState]

One of the toughest questions I have ever come across. I am completely baffled and for no apparent reason. I need some help so I found this forum.

What are the pHs of solutions A and C?

(All solutions are at 25 degrees C and assume all volumes are additive)

Solution A 50.0 ml of a 0.100 M solution of the weak monoprotic acid HZ
Solution B A 0.0500 M solution of the salt NaZ has a pH of 10.02
Solution C is made by adding 15.0 ml of .250 M KOH to solution A

This is what I've done so far, I don't know if any of it should have been done.

A+C

65.0ml = .065L

.250 M KOH * .065L = .01625 mol KOH
.100 M HZ   * .065L = .0065 mol HZ

Solution B

10^(-10.02) NaZ = 9.55 EE -11 M
[Z-] = 9.55 EE -11 / [Na+]

Any and all help would be appreciated, thank you.

[enahs]

I am a little confused. You say the question asks for the pH of solution A and B, but you are given the pH of solution B (which you could use to solve for the Ka or Kb of the acid)?

[AState]

Sorry I meant to ask for A and C. I'll edit the post.

[Borek]

Solution B lets you calculate Kb/Ka of HZ, then solution C is just a buffer with pH described by the Henderson-Hasselbalch equation.