Chapter 12, Problem 12.26P

Interpretation Introduction

Interpretation:

The sudden colour change of titration mixture at the end point of the titration by indicator should be explained.

Concept introduction:

Indicator:

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 with naked eyes the completion of titration reaction – the titrant and the analyte becoming equal in stoichiometric proportion, hence we use a chemical compound called indicator, which indicates the end of the reaction by color change.

The chemical compound which is used as indicator is capable of exhibiting different color in different $\text{pH}$ range.  The end point refers to the color change and indicates equivalence point has been reached.