Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: cz on November 25, 2009, 12:54:29 PM

Title: Hi, can someone please help me with the titration curve question for weak acid?
Post by: cz on November 25, 2009, 12:54:29 PM

Hi everyone:
  I got this lab for the titration curve, and the lab is trying to find the neutralization equation for acetic acid and NaOH.
then we are asked to calculate the Ka for the dissociation of the acetic acid, and the pH will be determined by doing the lab, how should I calculate the Ka?  And I'm really confused what this lab is doing, please *delete me*!

Title: Re: Hi, can someone please help me with the titration curve question for weak acid?
Post by: renge ishyo on November 25, 2009, 05:16:45 PM

You can get the pKa directly from your graph. First find the volume of the endpoint (the point where the slope of your graph changes most abruptly from low PH to high pH). Next, divide the endpoint volume by 2 to get the volume added halfway to the endpoint. The pH at the volume halfway to the endpoint is equal to the pKa. You can find the Ka from pKa = -log[Ka] or solving for Ka: 10^-pKa = Ka.