NCERT Class 10 Chapter 3 Carbon CBSE Board Sample Problems Short Answer (For CBSE, ICSE, IAS, NET, NRA 2022)

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What is denatured alcohol?

Why is ethanol denatured?

State any two uses of ethanol.


Ethanol when mixed with toxic substances like methanol is known as denatured alcohol.

Ethanol is denatured to make it unfit for drinking purposes so that alcohol for industrial purposes is not misused.

It is used to make cough syrups and it՚s used as an additive to petroleum.


Write the structural formula of:


Propanoic acid




Propanoic acid:



Write the chemical equation for the reaction that takes place when ethanol is mixed with ethanoic acid in presence of an acid.

What is the name given to such reactions?

Write any two uses of the product formed in these reactions.


Esterification reactions

The esters formed in these reactions are used in making perfumes and favouring agents.


Name the functional group of organic compounds that can be hydrogenated.

With the help of suitable example, explain the process of hydrogenation mentioning the conditions of the reaction and any one change in physical property with the formation of the product. Name any one natural source of organic compounds that are hydrogenated.


The functional groups of organic compounds that can be hydrogenated are alkenes and alkynes.

Unsaturated hydrocarbons undergo addition reactions with hydrogen in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons.

During this reaction, unsaturated compounds like vegetable oils which are in liquid state are converted to animal fats in solid state. Vegetable oil is an example of natural source of organic compound that are hydrogenated.


List in tabular form three physical and two chemical properties on the basis of which ethanol and ethanoic acid can be differentiated.


Difference in physical properties:


  • It exists only in liquid form.
  • It belongs to the functional group alcohols.
  • It has a specific smell but not like vinegar.


  • It can exist both in liquid as well as solid form,
  • It belongs to the functional group carboxylic acids.
  • It smells like vinegar.
  • Difference in chemical properties:


  • Reaction with sodium bicarbonate: No salt formation occurs and carbon dioxide gas is also not evolved.
  • It does not give litmus test i.e.. , no change in the colour of litmus solution.


  • Reaction with sodium bicarbonate: It will react with sodium bicarbonate to form a salt and carbon dioxide gas will be released.
  • It turns blue litmus red.


Differentiate between saturated and unsaturated hydrocarbons.


Saturated hydrocarbons:

A hydrocarbon in which each carbon atom is attached to four other atoms, is known a saturated hydrocarbon. The bonds so formed are single covalent bonds.

These hydrocarbons are also called alkanes.

Unsaturated Hydrocarbons: Hydrocarbons contains either a carbon-carbon double bond (C = C) or a carbon- carbon triple bond in their molecules are called unsaturated hydrocarbons


A compound has molecular formula . It can be used as a fuel. Identify the name of the compound and functional group present in it. Write the reaction involved in the conversion of this compound into Ethanoic Acid.


The compound is Ethanol

Functional group is - OH (alcohol)


a) Which type of organic compounds under goes addition reaction?

b) Mention the industrial application of addition reaction.


a) Unsaturated hydrocarbons undergo addition reaction.

b) An example of industrial application of addition reaction is Hydrogenation of vegetable oils using a nickel catalyst.


Name the following:

Third member of alkane series

Next higher homologue of Methanoic acid


a) Propane,

(b) Ethanoic acid,


a) Define Homologous series.

b) Give reasons β€”

i) Why are most carbon compounds poor conductors of electricity?

ii) Have low melting and boiling points?


a) A series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a homologous series.

b) (i) Most carbon compounds are poor conductors of electricity because no ions or charged particles are formed.

(ii) They have low melting and boiling points due to weak covalent bonds.


What is Methane? What happens when this compound burns in oxygen?


Methane is the simplest hydro carbon () . When methane burns in oxygen, carbon-di-oxide and water are produced.


Distinguish between Ethanol and Ethanoic acid on the basis of

a) Blue litmus test

b) Reaction with sodium bicarbonate

C) Reaction with Sodium metal (3)



  • Blue litmus test
  • Reaction with Sodium bicarbonate
  • Reaction with Sodium metal


  • No change
  • No reaction
  • Sodium Ethoxide is formed

Ethanoic Acid

  • Turns blue litmus red
  • Sodium Acetate is formed
  • Sodium Ethanoate is formed