Question

Which substance chars when heated with conc.$$H_{2}S{O}_4$$?
A) Carbohydrate
B) Hydrocarbon
C) Fat
D) Protein

Answer 1

Hint: We have to know that sulfuric acid is a mineral acid consisting of sulfur, hydrogen and oxygen atoms. We have to remember that the acid is colorless and odorless which can be diluted with all concentration of water. The molar mass of sulfuric acid is $98g/mol$ and sulfuric acid is used in the manufacturing of many chemicals.

Complete answer:
We will look at all the options to answer this question.
Option A) this is a correct option as when carbohydrate is heated with concentrated sulfuric acid it results in charring. We can confirm this test in labs also. When any sugar such as glucose, sucrose and other carbohydrates results in charing when heated with sulfuric acid.
Option B) this is an incorrect option as on heating hydrocarbons with sulfuric acid it does not lead to charring. For example when an alkene is reacted with concentrated sulfuric acid it will produce alkyl hydrogen sulfates.
Option C) this is an incorrect option as when a fat is heated with sulfuric acid it will produce color and not charring thus this option is not correct.
Option D) this is an incorrect option as on heating proteins with concentrated sulfuric acid it will not lead to charring.

The correct answer is option A.

Note:
When we add concentrated sulfuric acid to sugar the result is interesting. The sulfuric acid is a dehydrating agent and it dehydrates the carbohydrate sugar, removing the water and heating it into steam leaving behind the carbon foam. That’s why it looks black.