Question

What does the measured pH of a 1:1 buffer in a titration correspond to?

a) The pH at which the indicator changes color (titration endpoint).
b) The pKa of the acetic acid.
c) The pH at equivalence in the acetic acid-sodium hydroxide titration.
d) None of the possible answers are correct.
(Note: Select the most appropriate option.)

Answer 1

The measured pH of a 1:1 buffer in a titration corresponds to the pKa of the weak acid in the buffer solution, which is the midpoint of the titration curve.

Step-by-step explanation:

The measured pH of a 1:1 buffer in a titration generally corresponds to the pKa of the weak acid in the buffer solution.

This occurs at the midpoint of the titration curve, where the concentration of the acid equals the concentration of its conjugate base.

As discussed in the provided information, the selection of a suitable acid-base indicator is crucial in a titration since the indicator's color change should be close to the expected pH at the equivalence point.

For weak acids like acetic acid, methyl red is a suitable indicator because its pKin value is close to acetic acid's pKa.

The pH at the equivalence point, however, is different from the pKa and is dependent on the strength of the acids and bases involved in the titration.