Resolved Question

Is Thymol blue a suitable indicator for the following titrations?
Is Thymol blue (pKa=8.9) suitable indicator for each of the following titrations?

a) 0.10M HCL versus 0.10M KOH
b) 0.10M CH3COOH versus 0.10M KOH?
c) 0.10M HNO3 versus 0.10m NH3?


by joeyeehu...

Best Answer - Chosen by Asker
The choice of an indicator depends on the pH when the equivalent point is achieved.
The pH when the equivalent point is achieved must coincide with the pH range of the indicator.

a) is a titration of strong acid and strong base.
The equivalent point occurs between pH 3 to 10.

b) is a weak acid and strong base. The equivalent point occurs between pH 7 to 13

c) is a strong acid and a weak base. The equivalent point occurs between pH 3 to 7.

Hence, thymol blue (pKa = 8.9) is suitable to be used in (a) and (b) as it will change colour when the equivalent point is reached.


(c) is not suitable because it wont change colour eventhough the equivalent point is reached,.