Thursday
August 21, 2014

Homework Help: chemistry - titration

Posted by phil on Sunday, August 5, 2007 at 2:11pm.

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

Please explain your answer. Thank you.

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.

Answer this Question

First Name:
School Subject:
Answer:

Related Questions

Chemistry - Part A: Unknown Acid use 1gram and mix with 120 mL of distilled ...
Chemistry - Consider a weak acid-strong base titration in which 25.0 mL of 0.100...
Chemistry - During an acid-base titration, 25 mL of NaOH 0.2 M were required to...
Chemistry (Titration Curves) - Which of the following Acid+Base titration ...
Chemistry - I there, this is my lab worksheet, I am having trouble filling it ...
chemistry - You weigh a sample of a monoprotic unknown acid and dissolve it in ...
College Chemistry - I need help with this question!! a sample of pure KHP ...
Chemistry, pH, Buffers - Please help!! Given this data: mass of unknown acid 1....
chemistry - Suppose that 0.483 g of an unknown monoprotic weak acid, HA, is ...
Analytical Chemistry 2 - Consider the titration of the weak acid HA with NaOH. ...

Search
Members