# chemistry - titration

posted by .

Show that for the titration of a weak acid, HA, with NaOH solution, at half-titer, pH = pKa.

HA + NaOH ==> NaA + HOH

Ka for HA = (H^+)(A^-)/(HA) and solve for H^+.
(H^+) = Ka*[(HA)/(A^-)
When HA is half neutralized, an equal amount of NaA has been formed, therefore, (HA) = (A^-) at the half-way point of the titration. (You can prove this over and over by starting with ANY volume of HA and adding half that volume of an equimolar NaOH solution.)Therefore, the term (HA)/(A^-) = 1 and
(H^+) = Ka
Take the negative log of both sides
-log(H^+) = -log Ka
pH = pKa.

## Similar Questions

1. ### CHEMISTRY FOR DR. BOB or anyone else

A hypothetical weak acid HA, was combined with NaOH in the following proportions: 0.20 mol HA, 0.08 mol NaOH. The mixture was then diluted to a total volume of 1L, and the pH measured. (a) If pH=4.80, what is the pKa of the acid (b) …
2. ### Chemistry

Part A: Unknown Acid use 1gram and mix with 120 mL of distilled water Determine the concentration of the acid by titrating with 0.0998 M of NaOH Concentration of NaOH= 0.0998M Volume of NaOH= 3.5 mL # moles of NaOH= Initial Concentration …
3. ### Chemistry

I there, this is my lab worksheet, I am having trouble filling it out. Please help me with it. Expt #1- Molecular Weight of Unknown Acid Unknown Acid: #3 Mass of Unknown solid acid transferred:1.0g Volume of volumetric flask: 100.00 …
4. ### Chemistry

Consider a weak acid-strong base titration in which 25.0 mL of 0.100 M acetic acid is titrated with 0.100 M NaOH. a) Calculate the pH after the addition of 3.00mL of NaOH. b) What is the pH of the solution before the addition of NaOH …
5. ### Chemistry (Titration Curves)

Which of the following Acid+Base titration combinations would have a buffering region in their plot?
6. ### College Chemistry

I need help with this question!! a sample of pure KHP weighing .8097g dissolved in water and titrated with 40.25 mL of NaOH solution. The same NaOH solution was used to titrate a solution of a weak diprotic acid H2X. A sample of 0.18694g …
7. ### chemistry

You weigh a sample of a monoprotic unknown acid and dissolve it in 50.00 mL of distilled water. Exactly half of this solution is titrated with Sodium Hydroxide to the phenolphthalein end point. The pH of the other half of the original …
8. ### Chemistry

During an acid-base titration, 25 mL of NaOH 0.2 M were required to neutralize 20 mL of HCl. Calculate the pH of the solution for each: a) Before titration b) After adding 24.9 mL of NaOH c) At equivalence pt d) After adding 25. 1 …
9. ### chemistry

You discovered a new diprotic acid, which you have named edmontonic acid. You want to characterize the pKa’s of edmontonic acid, so you perform a titration experiment. Your data are summarized in the table below. Your titration sample …
10. ### Chemistry

In the titration of a solution of a weak acid HA with NaOH the pH is 5.0 after 10ml of NaOH solution has been added and 5.6 after 20ml of the NaOH solution has been added. Find the PKa of HA?

More Similar Questions