Question

Which of the following indicators is an olfactory indicator?
A.Litmus
B.Vanilla
C.Turmeric
D.Phenolphthalein

Answer 1

Hint: Basically, an olfactory indicator is a substance whose smell varies depending on whether it is mixed with an acidic or basic solution. Moreover, these indicators can be used in the laboratory to test whether a solution is a base or an acid.

Complete step by step answer:
Basically, a substance that can be added to the reaction mixture to indicate the equivalence point of the titration is known as an indicator. These are weak acids or weak bases that have distinctly different colors in their ionized and non-ionized forms.
Moreover, colored indicators are often used to measure the pH. These indicators often give different colors in basic and acidic environments. For example, litmus is blue in the basic environment and red in an acidic environment. Now, in case of phenolphthalein, if we use this as an indicator in which a strong base is used as a titrant and acid as the substance titrated, then it would give a color change from colorless to pink in the reaction flask near the equivalence point.
Now, let’s discuss olfactory indicators. These are certain substances whose smell changes in acidic or basic solutions. The change in odor helps us in detecting whether a given sample solution is acidic or basic in nature. Some of the examples of these types of indicators are vanilla extract, onion and clove oil.

Hence, option B is correct.

Note: The vanilla extract has a characteristic pleasant smell. However, an acidic solution does not destroy the smell of vanilla extract whereas a basic solution does. Moreover, in case of onion and cloves the smell is retained in the acidic solutions.