Question

Which of the following pH indicator ranges would be the most useful for the titration of a weak base with a strong acid?

A) 4-6 (methyl red)
B) 7-8
C) 5-8
D) 8-10

Answer 1

For the titration of a weak base with a strong acid, methyl red (option A) with a pH range of 4-6 is the most appropriate indicator since it has a pKa value less than 7, which is close to the pH level at the equivalence point.

Step-by-step explanation:

The most useful pH indicator range for the titration of a weak base with a strong acid would be one where the indicator's pKa is close to the pH at the equivalence point of the titration. For a weak base-strong acid titration, the pH at the equivalence point will be less than 7. Therefore, an indicator with a pKa less than 7 should be used. Among the given options, methyl red, with a pH range of 4-6, would be the most appropriate because its pKa is below 7, aligning with the expected pH at the equivalence point.