Question

____ is a natural indicator.
A.Methyl orange
B.Litmus
C.Phenolphthalein
D.All of above

Answer 1

Hint: Just like the name suggests indicator can be defined as any substance which will help in indicating a change.The change could be anything either a physical change or some chemical change.Physical changes often tend to affect the physical form eg- of substances but not its chemical composition whereas when a chemical change occurs the substance experiences a change in it’s chemical composition eg-bonds formed,transfer of electrons.

Complete answer:
From an academic perspective indicators can be defined as substances which show a change in color when brought in contact with acids and bases.Depends on source from which the indicator is made,indicators can be categorised into two different categories-Natural indicators and Synthetic indicators.Natural indicator is a substance which is found naturally and can determine whether the substance is acidic or basic.A natural indicator that is used most commonly is litmus which is extracted from lichens.It is available either in the form of solution or in the form of paper strips known as litmus paper.Few other examples of natural indicators include turmeric, grape juice, red cabbage, cherries, onion, beetroot etc. The indicators which are synthesized in the laboratory are known as synthetic indicators.Few examples of synthetic indicators include phenolphthalein, methyl orange etc.
By referring to our discussion we can conclude that the correct option is option B, Litmus.

Note:
Litmus appears like a purple dye.It turns red in acidic solution and blue in basic solution. Indicators are often used in laboratories for qualitative and quantitative analysis.They can be also used to notify about the pH changes which occur in a chemical reaction.