Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: diane on June 07, 2013, 06:19:31 PM

Title: Find Ka of an indicator
Post by: diane on June 07, 2013, 06:19:31 PM

What is the Ka of thymolphthalein indicator?

The indicator has a range of pH's so how can I find the Ka?

Title: Re: Find Ka of an indicator
Post by: Borek on June 08, 2013, 03:18:00 AM

http://www.titrations.info/acid-base-titration-indicators-preparation

Color changes in a pH range, but pKa is a single number, see discussion here:

http://www.titrations.info/acid-base-titration-indicators

pKa determination doesn't depend on the fact you are dealing with an indicator, all that matters is that you are dealing with a weak acid (or base).