Carbon and its Compounds NCERT Solution, study material, CBSE Notes

NCERT Solution: Carbon and its Compounds

A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?

2HC ≡ CH + 5O₂ → 4CO₂ + 2H₂O + Heat
When ethyne is burnt in air, it gives a sooty flame. This is due to incomplete combustion caused by limited supply of air. However, if ethyne is burnt with oxygen, it gives a clean flame with temperature 3000�C because of complete combustion. This oxy-acetylene flame is used for welding. It is not possible to attain such a high temperature without mixing oxygen. This is the reason why a mixture of ethyne and air is not used.

How would you distinguish experimentally between an alcohol and a carboxylic
acid?

We can distinguish between an alcohol and a carboxylic acid on the basis of their reaction with carbonates and hydrogen carbonates. Acid reacts with carbonate and hydrogen carbonate to evolve CO₂ gas that turns lime water milky.

Alcohols, on the other hand, do not react with carbonates and hydrogen carbonates.

What are oxidising agents?

Oxidising agents are the substances that gain electrons in redox reaction and whose oxidation number is reduced.

Would you be able to check if water is hard by using a detergent?

Detergent gives lather with hard and soft water both, while a soap gives lather with soft water only. Thus, it is not possible to check if water is hard; by using a detergent.

People use a variety of methods to wash clothes. Usually after adding the
soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a
brush or the mixture is agitated in a washing machine. Why is agitation
necessary to get clean clothes?

A soap molecule has two parts namely hydrophobic and hydrophilic. With the help of these, it attaches to the grease or dirt particle and forms a cluster called micelle. These micelles remain suspended as a colloid. To remove these micelles, it is necessary to agitate clothes.

Ethane, with the molecular formula C₂H₆ has

Ethane, with the molecular formula C₂H₆ has
(a) 6 covalent bonds.
(b) 7 covalent bonds.
(c) 8 covalent bonds.
(d) 9 covalent bonds.

Ans (b) 7 covalent bonds.

Butanone is a four-carbon compound with the functional group

Butanone is a four-carbon compound with the functional group
(a) carboxylic acid.
(b) aldehyde.
(c) ketone.
(d) alcohol.

Ans (c) ketone.

While cooking, if the bottom of the vessel is getting blackened on the outside, it means that

While cooking, if the bottom of the vessel is getting blackened on the outside, it means that
(a) the food is not cooked completely.
(b) the fuel is not burning completely.
(c) the fuel is wet.
(d) the fuel is burning completely.

ANS (b) the fuel is not burning completely.