Question

How can indicators be used to test for the presence of different organic molecules?

Answer 1

First of all you have to know about the indicators, and indicators are those chemical species which are used to show the presence of different organic molecules in the given substance by changing their appearance or smell.

Complete answer:
From the above definition it is clear that by changing the original form i.e. color or odor an indicator is used to test for the presence of different organic molecules in the following manner:
-Schiff’s reagent is a type of indicator which is used to test for the presence of aldehydes in the given solution. Schiff’s reagent is a colorless solution which changes its color to magenta pink in the presence of aldehyde.
-Bromine water is also a type of an indicator which is used to test for the presence of unsaturated organic compounds in the given solution. As the appearance of bromine water is brown but in the presence of unsaturated compounds it loses its color and gives indication for the presence of unsaturated organic molecules.
-Some other examples of indicators which are used to test for the presence of organic compounds are Fehling solution, Tollen’s reagent, etc.

Note:
Here some of you may think that indicators are only used to distinguish between an acid and a base solution, but this assumption is not true. Indicators are also used to test the presence of organic compounds in any substance.