Question

A best indicator for acid base titration is when the pKa of the indicator match with   
a. the pKb of the analyte     b. the pH at half equivalence point c. the pKa of the analyte
d. the pH at the equivalence point   e. the pOH at half equivalence point

Answer 1

D) the best indicator to choose would be the one whose pKa will be closer to the pH at the equivalence point.

Reason: Generally the change in color at the end point is very fast and you might miss the continuous change occurring in the color of the sample.

The change is brought by that extra whole drop of the titrant that is being added to the solution.

Hence to keep the error margin of the pH negligible it is advisable that one should select pKa of the indicator as close as possible to the pH at the equivalence point.