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Why are indicators added to the sample solution in many titrations?
ATo make the end point visible by a colour change
BTo speed the reaction between titrant and analyte
CTo dissolve any solid particles left in the sample
DTo keep the solution at a steady temperature value
Answer & Solution
Correct answer: A. To make the end point visible by a colour change
1. The equivalence point must be detected somehow if the titrant volume is to be useful.
2. Sometimes the reaction itself shows a change, as when bubbling stops in the vinegar test.
3. More often a special dye called an indicator is added.
4. It changes colour at or very near the equivalence point, marking the end point.
5. Indicators are used in small amounts and are not there to alter reaction speed.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.5 Quantitative Chemical Analysis_
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