In: Chemistry
The anthocyanin in hydrangeas can be isolated and used as an environmentally friendly pH indicator for titrations. At the end of a titration reaction of a strong acid with a strong base, you have a neutral solution. What color do you expect anthocyanin to be at the end of a titration? Describe a lab experiment to support your prediction.
At the end of a titration reaction of a strong acid with a strong base, we have a neutral solution. At the end of a titration the color of anthocyanin will be purple.
Describe a lab experiment to support your prediction-
Titrations of 0.1 M NaOH and 0.1 M H2SO4 (strong acid-strong base titration),using Anthocyanins as a natural pH indicator.
A strong acid and strong base both ionizes completely in solution. Therefore, when a strong acid is combined with a strong base it produces a salt
H2SO4 (aq) +2 NaOH (aq) --------à Na2SO4 +2H2O (l)
Since the Na2SO4 produced has no effect upon pH, when an equivalent amount of NaO H is added to a solution of H2SO4 the solution has a neutral pH (i.e. pH = 7.0)
This anthocyanin will be red at low pH value. It will be purple in neutral solution. It will be greenish-yellow if the solution is basic. We have to titrate until the color of the solution is purple.