[Aegis6]

In a postlab for an experiment I recently did involving the titration of Potassium Hydrogen Phthalate with Sodium Hydroxide to standardize the NaOH, it wants for me to determine the molarity of the NaOH solution from the pH of the system at the equivalence point. I have tried to do this several different ways but I keep ending up with values that are incredibly far away from the expected range. Could anyone tell me how to solve this?

[Arkcon]

Per forum rules you should show your attempts at solving the problem before receiving help.

You will have to show us your data and your calculations if we're going to help at all.

[Aegis6]

The initial pH of the KHP was 4.01 and the pH at the equivalence point was 8.5. There was approximately 50mL of KHP and 26.5 mL of the NaOH was titrated into it.

-At first I tried to use the pH to determine pOH and from there calculate the molarity of the dissociated NaOH which I thought I could use to lead back to the original molarity of the NaOH, but I found the [OH-] to be 3.16e-6M but was unable to determine how to proceed from there.
-Then I tried a new route, using the initial pH and the equivalence pH to find the moles of H+ used up, setting that value as equal to the NaOH consumed (assuming a 1:1 ratio). This led me to 4.886e-6 moles of NaOh being consumed which ended up being 1.84e-4M solution.

The range we were told to anticipate was around 0.01M, and while some deviation was expected I am pretty sure these results are wildly off. I feel like an ICE table may be necessary but I am really unsure of how to proceed from here.

[Borek]

it wants for me to determine the molarity of the NaOH solution from the pH of the system at the equivalence point

Are you sure that's what you are asked to do? What is the exact wording?

Generally speaking equivalence point pH doesn't depend on the NaOH concentration (only indirectly, through the dilution factor). Using it to calculate the concentration makes no sense.

[Aegis6]

"Using the pH at the equivalence point as determined from your titration curve, find the unknown concentration of your NaOH solution."

[Borek]

Strange. As explained earlier, pH is not the way of dealing with such problems, you should use stoichiometry.