Bromothymol blue makes something yellow when it is acidic, and blue when it it an alkaline (green when neutral). I know acid has hydrogen ions, and alkaline has hydroxide. How does it work? I found out it reacts with carbonic acid, but does it have anything to do with the pH level of something?
-Thanks
In: Chemistry
The Bromothymol blue molecules slightly change structure when reacting with protons / hydrogen ions. This structural change results in a change in the optical properties of the molecule – In particular, each molecule becomes more “conjugated” meaning there is a higher number alternating single and double bonds. The degree of conjugation in a molecule contributes to it’s optical properties.
The colour observed is of the Bromothymol blue molecules themselves, rather than the Bromothymol blue molecules changing the colour given by the molecules of the substance it is being added to.
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