Chapter 11, Problem 11.36P

Interpretation Introduction

Interpretation:

The origin of thumb rule that states color change of the indicator occurs at $p{K}_{HIn}\pm 1$ has to be explained.

Concept introduction:

Equivalence point ensures the titration reaction becomes completed and at this point the number of moles of titrant and the number of moles of analyte remain equal.  We cannot see the completion of titration reaction – the titrant and the analyte becoming equal in stoichiometric proportion, hence we use a chemical compound called indicator called which indicates the end of the reaction by color change. The end point refers to the color change and indicates equivalence point has been reached.