[Boxxxed]

A 0,1276g sample of an unknown monoprotic acid is dissolved in 25,0ml of water and titrated with a 0,0633M NaOH solution. It takes 18,4 ml to neutralize the acid and after 10,0 ml of base is added during titration, the pH has a value of 5,87. What is the pKa of the unknown acid?

I've done this before but I don't remember how. Could someone explain what is happening?

I have
moles of unknown acid
moles of base added
moles excess base added

[rabolisk]

What's happening is acid-base neutralization. I could give you a step by step instruction on what to do, but it's better for you to figure out on your own. Write out the reaction that is happening, and remember what neutralization means.

[Boxxxed]

I've tried the question in different ways but I'm not coming up with the right answer.


0.001165 mol acid
0.001798 mol base
1.35x10^-6 = H3O

Subbing into Ka=(Base)(H3O)/(Acid) I get pka = 5.68 but this isn't the right answer.

[Boxxxed]

In this question..

What is the pH of the solution at the equivalence point in the titration of 100 mL of 0.100 M ammonia with 0.100 M HCl solution.

For this question all of the ammonia forms NH4 and the pH can be calculated using given pKa and concentration.


Not sure what is happening in the original question though

Also, I would have thought the excess 10 mL of NaOH to form OH- and determine the pOH--->pH but it doesn't for some reason

[Borek]

Please don't mix different questions in one thread - at the moment I have no idea which information is for which question and I am not going to try to guess.

Are you sure it was EXCESS NaOH?

[rabolisk]

Start from step 1. Write out the reaction that is happening, and remember what neutralization means.

[Boxxxed]

I will come back to this question