NCERT Solutions for Class 10 Science Chapter 4 Carbon and Its Compounds

NCERT solutions for class 10 science chapter 4 Carbon and its compounds

Topic:4.1 Bonding in carbon - The covalent bond

Q.1. What would be the electron dot structure of carbon dioxide which has the formula ?

Answer:

The electron dot structure of carbon dioxide which has the formula is:

Q.2. What would be the electron dot structure of a molecule of sulphur which is made up of eight atoms of sulphur? (Hint – The eight atoms of sulphur are joined together in the form of a ring)

Answer:

The electron dot structure of a molecule of is:

NCERT Textbook Solutions for Class 10 Science Chapter 4 Carbon and Its Compounds

Topic 4.2: Versatile nature of carbon

Q.1. How many structural isomers can you draw for pentane?

Answer:

There are three structural isomers of pentane:

n-pentane
iso-pentane
neo-pentane

Q. 2. What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?

Answer:

The two properties of carbon which lead to the formation of a large number of carbon compounds are:

( 1) Catenation: Carbon has the unique ability to form bonds with other atoms of carbon which gives rise to large molecules. The carbon-carbon bond is very strong and hence stable.

(2) Tetravalency: Since carbon has a valency of four, it is capable of bonding with four other atoms. These bonds that carbon forms with other elements are very strong making these compounds exceptionally stable.

Q.3. What will be the formula and electron dot structure of cyclopentane?

Answer:

The formula of cyclopentane is .

And, the electron dot structure of cyclopentane is :

Q. 4. Draw the structures for the following compounds.

(i) Ethanoic acid

Answer:

The structure of ethanoic acid is:

Q. 4. Draw the structures for the following compounds.

(ii) Bromopentane

Are structural isomers possible for bromopentane?

Answer:

The structure of bromopentane( ) is:

Yes, structural isomers for bromopentane is possible.

For n-pentane: Br at carbon

Also, Br at different carbons for iso-pentane and neo-pentane.

Q. 4. Draw the structures for the following compounds.

(iii) Butanone

Answer:

The structure of Butanone ( ) is:

Q. 4. Draw the structures for the following compounds.

(iv) Hexanal

Answer :

The structure of hexanal ( ) is:

Q. 5. (i) How would you name the following compound?

Answer :

The compound ( ) has 2 carbon atoms. Hence the parent hydrocarbon is ethane.

A bromo group is attached to one of the carbon atoms. Thus, the nomenclature of the compound is Bromoethane.

Q. 5. (ii) How would you name the following compounds?

Answer:

The compound ( ) contains 1 carbon atom. Hence the parent hydrocarbon is methane. It contains the functional group aldehyde.

Thus, the nomenclature of the compound is: Methanal.

Q.5. (III) How would you name the following compound?

Answer:

The compound has 6 carbons in the chain. Hence the parent hydrocarbon is hexane. It contains a triple bond and hence the suffix -yne- is used. Thus, the nomenclature of the compound is: Hexyne

Topic 4.3 Chemical Properties of carbon compounds

Q. 1. Why is the conversion of ethanol to ethanoic acid an oxidation reaction?

Answer:

The conversion of ethanol to ethanoic acid is :

Since there is an addition of oxygen in the reaction, this is an oxidation reaction.

Q. 2. A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?

Answer:

A mixture of oxygen and ethyne is burnt for welding. But a mixture of ethyne and air is not used. This is because ethyne undergoes incomplete combustion in air giving a sooty flame.

In oxygen, ethyne gives a clean flame with temperature as high as 3300 K due to complete combustion.

Topic 4.4: Some Important Carbon Compounds - Ethanol and Ethanoic Acid

Q. 1. How would you distinguish experimentally between an alcohol and a carboxylic acid?

Answer:

We can distinguish between alcohol and carboxylic acid by reacting them with carbonates/hydrogen carbonates. The acid reacts with hydrogen carbonate to liberate carbon dioxide which turns lime water milky.

Whereas alcohol shows no evolution of gas when reacted with carbonates.

Q.2. What are oxidizing agents?

Answer:

The oxidation reaction is the reaction in which oxygen is added or hydrogen is removed.

The substance which adds oxygen to others is known as oxidizing agents.

Example : AlkalinepPotassium permanganate

Topic 4.5: Soaps and Detergents

Q.1. Would you be able to check if the water is hard by using a detergent?

Answer:

No, we will not be able to check if the water is hard sing detergents. This is because detergents give rich lather with both hard and soft water without forming any scum.

Q. 2. 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?

Answer:

Soap molecules form spherical structures known as micelles. The oily dirt is trapped inside these micelles which remain suspended as colloid. Hence, to remove these micelles containing the dirt, the clothes are agitated.

NCERT solutions for class 10 science chapter 4 Carbon and its Compounds - Exercise solutions

Q. 1. Ethane, with the molecular formula has

(a) 6 covalent bonds.
(b) 7 covalent bonds.
(c) 8 covalent bonds.
(d) 9 covalent bonds.

Answer:

Ethane, with the molecular formula has 7 covalent bonds.

(b) It has 1 ( ) and 6( ) bonds.

Q. 2. Butanone is a four-carbon compound with the functional group

(a) carboxylic acid.
(b) aldehyde.
(c) ketone.
(d) alcohol.

Answer:

Butanone is a four-carbon compound with the functional group ketone. (c)

Butan- one : one is the suffix used for the functional group ketone.

Q. 3. 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.

Answer:

While cooking, if the bottom of the vessel is getting blackened on the outside, it means that the fuel is not burning completely.

(b) is the answer

Q. 4. Explain the nature of the covalent bond using the bond formation in.

Answer:

Carbon has four electrons in its outermost shell and needs to gain or lose four electrons to attain noble gas configuration. Carbon overcomes this problem by sharing its valence electrons with other atoms of carbon or with atoms of other elements.

Of the four electrons, three are shared with hydrogen atoms and one with a chlorine atom. Thus it has three (C-H) and one (C-Cl) covalent bonds.

These bonds formed by the sharing of electrons are known as covalent bonds. Carbon, hydrogen, and chlorine attains the nearest noble gas configuration of Ne, He and Ar respectively.

Q.5. (a) Draw the electron dot structures for

• ethanoic acid .

Answer:

The electron dot structure of ethanoic acid ( ) is:

Q.5. (b) Draw the electron dot structures for

• .

Answer:

The electron dot structure of hydrogen sulphide ( ) is:

Q.5.(c) Draw the electron dot structures for

• propanone .

Answer:

The electron dot structure of propanone ( ) is:

Q.5.(d) Draw the electron dot structures for

Answer:

The electron dot structure of is:

Q. 6. What is a homologous series? Explain with an example.

Answer:

A series of carbon compounds having different numbers of carbon atoms but have the same functional group substituting the hydrogen atom is known as a homologous series.

For example, methane, ethane, propane, butane, etc. constitute the alkane homologous series. The general formula for alkanes is . Methane ; Ethane ; Propane and so on.

Q. 7. How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?

Answer:

Physical Properties

Chemical Properties:

Ethanol	Ethanoic acid
It has no action on litmus paper.	It turns blue litmus to red.
no reaction with	Liberates when reacted with

Q. 8. Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?

Answer:

A soap is a sodium or potassium salt of long-chain fatty acids. It has one polar hydrophilic end and one non-polar hydrophobic end. These molecules have a unique orientation inside water in form of clusters of molecule in which hydrophobic ends are in the interior of the cluster and ionic ends on the surface of cluster thus keeping the hydrocarbon portion out of water. This formation is known as Micelle. Soap in the form of a micelle is able to clean, as the oily dirt is collected in the centre of the micelle.

No, micelle formation does not take place in ethanol because the alkyl chain of soap becomes soluble in alcohol.

Q. 9. Why are carbon and its compounds used as fuels for most applications?

Answer:

Carbon compounds have high calorific values. Therefore, carbon and its compounds are used as fuels for most applications. They give a lot of heat and light when burnt in air. Saturated hydrocarbons like methane burn with a clean flame without any smoke and are thus environmentally friendly.

Q. 10. Explain the formation of scum when hard water is treated with soap.

Answer:

Hard water contains calcium and magnesium salts. When soap is added with hard water, it reacts with the calcium and magnesium ions of hard water to form an insoluble substance called scum. To overcome this problem, detergents are used.

Q. 11. What change will you observe if you test soap with litmus paper (red and blue)?

Answer:

Soap is basic in nature and hence will turn red litmus blue. However it will have no effect on blue litmus paper.

Q. 12. What is hydrogenation? What is its industrial application?

Answer:

The conversion of unsaturated hydrocarbon to saturated hydrocarbon by the addition of hydrogen in the presence of nickel catalyst is called hydrogenation. This reaction is commonly used in hydrogenation of vegetable oil into vegetable ghee.

Q. 13. Which of the following hydrocarbons undergo addition reactions:

Answer:

Unsaturated hydrocarbons like alkenes and alkynes will undergo addition reactions. Therefore, (alkene having ) and (alkyne having ) will give addition reactions.

Q. 14. Give a test that can be used to differentiate between saturated and unsaturated hydrocarbons.

Answer:

Butter is a saturated compound and oil is an unsaturated compound.

Test: When oil is added to a test tube containing alkaline potassium permanganate solution , the pink colour of the solution disappear. Therefore, cooking oil causes decolourisation of the solution. This does not happen in case of butter.

Q. 15. Explain the mechanism of the cleaning action of soaps.

Answer:

A soap is a sodium or potassium salt of long-chain fatty acids. It has one polar hydrophilic end and one non-polar hydrophobic end. When soap is at the surface of the water, the hydrophobic tail of soap being nonsoluble in water protrudes out of the water with the ionic end in water.

When there is no more space for soap molecules on the surface, these molecules create a unique orientation inside water in form of clusters in which hydrophobic ends are in the interior of the cluster and ionic ends on the surface of cluster thus keeping the hydrocarbon portion out of water. This formation is known as Micelle.

Soap in the form of a micelle is able to clean, as the oily dirt is collected in the centre of the micelle.The ionic ends in the micelles remain attached to water. When the dirty clothes are agitated in a soap solution, the oily dirt particles entrapped by soap micelles get dispersed in water and the clothes get cleaned.