MG SCHOOL EDUCATION: Class 10 Science Chapter 4 Carbon and its Compounds

Class 10 Science

Chapter 4 Carbon and its Compounds

Previous years appeared questions

MULTIPLE CHOICE QUESTIONS

1. Number of single bonds found in the molecular structure of propanal is ( june 2022)

(A) 8 (C) 7 (B) 6 (D) 5

Ans. : (A) 8

2. Identify the correct electron dot structure of nitrogen molecule in the following : (Sep 2020)

3. The name and the molecular formula of the unsaturated hydrocarbon having general formula CnHn2 and containing 3 carbon atoms is (Sep 2020)

(A) propane, C3H8

(B) Cyclopropane, C3H6

(D) Propene, C3H6

Ans. : (D) Propene, C3H6.

4. An example for saturated hydrocarbon is (March 2020)

(A) C2H6

(B) C3H4

(D) C2H4

Ans. : (A) C2H6

5. The molecular formula of three carbon compounds which are in homologous series are C2H6, C3H8, C4H10. The suitable general formula for these compounds is (March 2020)

6. The functional groups present in propanol and propanal respectively are (March 2019)

(A) — OH and — CHO

(B) — OH and — COOH

(D) — CHO and — CO

Ans: (A) — OH and — CHO

7. The hydrocarbon that undergoes addition reaction among the following is : (KSEEB MQP 2020)

A. C2 H6 B. C3 H8 C. CH4 D. C3 H6

Ans: D. C3 H6

8. (April 2023)

ONE MARKS QUESTIONS

1. Write the structural formula of ethene molecule. (June 2022)

Ans. :

2. Can detergent be used to test hardness of water ? Give reason. (Sep 2020)

Ans. :

No,

Detergents give foam / lather with both hard water and soft water and do not form scum.

3. What is a covalent bond ? (june 2019)

Ans:

A covalent bond is a chemical bond in which pairs of electrons are shared between two atoms.

4. Name the first member of alkynes and write its molecular formula. (june 2019)

Ans:

> The first member of the alkyne family is Ethyne

> molecular formula is C2H2

5. Is it possible to test the hardness of water using detergents? Give reason for your answer. (KSEEB MQP 2020)

Ans:

No, because detergent gives lather with hard and soft water both, it is not possible to check if water is hard by using a detergent.

6. The general formula of cycloalkanes is CnH2n and its first member is cyclopropane (C₃H₆). Write the molecular formula and structural arrangement of the fourth member of this homologous series. (April 2023)

Ans.:

Molecular formula : C₆H₁₂

Structural arrangement

7. What is hydrogenation? (April 2023)

Ans.:

Hydrogen is added to unsaturated hydrocarbons in the presence of catalyst such as palladium or nickel to give saturated hydrocarbons. This is known as hydrogenation.

Conversion of unsaturated oils into saturated fats by adding hydrogen in the presence of palladium / nickel like catalyst.

8. Why are detergents more suitable for cleansing clothes in hard water? (June 2023)

Ans.: Detergents do not form insoluble precipitates with calcium / magnesium ions present in hard water

TWO MARKS QUESTIONS

1. Write the structure of Benzene and Propyne. (March 2020)

Ans. :

2. Explain substitution reaction in hydrocarbons with an example. (June 2019)

Ans:

> The substitution reaction is a reaction in which hydrogen atoms of a hydrocarbon are replaced by other atoms.

> example: Methane reacts with chlorine, in the presence of sunlight, to form chloromethane and hydrochloric acid.

sunlight

> CH4 + Cl2 → CH3Cl + HCl.

3. Explain the mechanism of cleaning action of soaps. (June 2019

Ans:

When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth. Then, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster. These micelles remain suspended in the water. The dust particles are then easily rinsed away by water.

4. The general formula of two specific groups of saturated and unsaturated hydrocarbons is Cn H 2n . Write the structures of the member of each group when n = 3. (June 2019)

Ans:

n=3, CnH2n = C3H6

5. What are structural isomers ? Name the first member of alkanes that shows structural isomerism. (March 2019)

Ans:

> Compounds with identical molecular formula but different structures are called structural isomers.

> First member of alkanes that shows structural isomerism is Butane

6. Name the Ketone having four carbon atoms and write its structure. (KSEEB MQP 2020)

Ans:

Butanone or Ethyl methyl ketone has four carbon atoms.

7. Explain combustion reaction of carbon compounds with an example. (KSEEB MQP 2020)

Ans:

Combustion means burning of carbon or carbon-containing compounds in the presence of air or oxygen to produce carbon dioxide, heat and light.

Ex:

2CH3OH + 3O2 → 4H2O + 2CO2

8. In a homologous series, the first member of hydrocarbon group has the molecular formula CH₄. Then find out the molecular formula of the fourth member and write two types of structural formula of it. (June 2023)

Ans.:

THREE MARKS QUESTIONS

1. Explain the addition and substitution reaction with the help of examples. C2H6 undergoes substitution reaction but not addition reaction. Why ? (March 2020)

> Unsaturated hydrocarbons combine with hydrogen atoms in the presence of catalysts to give saturated hydrocarbons.

> Example : Hydrogenation of vegetable oil.

addition reactions of alkenes / alkynes.

> In the presence of sunlight other group of atoms can replace hydrogen atoms one by one from carbon compounds.

> Example : In the presence of sunlight Chlorine replaces hydrogen atoms one by one from methane.

Methane + Chlorine → Chloromethane + Hydrogen chloride

CH4 + Cl2 → CH3Cl + HCl.

> C2H6 is saturated hydrocarbon. OR

> In C2H6 there will be single bond between carbon atoms / This is not an unsaturated compound. No hydrogen atoms can be added but hydrogen atoms can be substituted.

2. Explain how soap cleans clothes. More amount of soap is required to clean the clothes in hard water. Why ? (March 2020)

> The molecules of soap are sodium or potassium salts of long chain carboxylic acids.

> The ionic end of soap interacts with water while the carbon chain interacts with oil.

> The soap molecules thus form structure called micells. This forms an emulsion in water.

> The soap micelles thus helps in pulling out the dirt in water and we can wash our clothes clean.

> The reaction of soap with calcium and magnesium salts in hard water develop scum ( precipitation, insoluble substance ). Hence we need large amount of soap to clean clothes in hard water.

3. (i) Write the differences between saturated and unsaturated hydrocarbons.

(ii) Write the molecular formula and structural formula of an alkene having five carbon atoms. (March 2019)

Ans:

(i)

(ii)

Molecular Formula: C5H10

Structural Formula:

4. (i) Carbon atom does not form C4- anion and C4+ cation. Why ?

(ii) How can ethanol be converted into ethanoic acid ? (March 2019)

Ans:

(i)

> Carbon cannot form C4+ cation because of removal of 4 elections from a carbon atom would require a large amount of energy.

> Carbon cannot form C4- anion because it would be difficult for the nucleus with 6 protons to hold on to 10 electrons.

(ii)

Ethanol is converted into ethanoic acid by the addition of oxygen released by potassium permanganate in the reaction mixture.

5. Write one difference between saturated carbon compounds and unsaturated carbon compounds. Carbon forms covalent bonds with other atoms but not ionic bonds. Why? Explain. (KSEEB MQP 2020)

Ans:

(Any one)

Because

> Carbon cannot form C4+ cation because of removal of 4 elections from a carbon atom would require a large amount of energy.

> Carbon cannot form C4- anion because it would be difficult for the nucleus with 6 protons to hold on to 10 electrons.

6. a) Identify unsaturated hydrocarbons in the following carbon compounds and write their structural formula. C₆H₆, C₅H₁₂, C₂H₅OH, C₂H₂

b) Write the difference between esterification and saponification. (June 2023)

Ans:

★ Esterification: Reaction between an acid and an alcohol to produce esters.

★ Saponification : Reaction between an alkaline base and long chain carboxylic acid to produce soaps [ or sodium / potassium salts of long chain carboxylic acid ]

7. a) Write electron dot structure of oxygen molecule.

b) Carbon atom does not form C⁴⁻ anion and C ⁴⁺ cation. Why? (June 2023)

Ans:

★ C⁴⁻ anion does not form because difficult for the nucleus with six protons to hold on ten electrons.

★ C⁴⁺cation does not form because require large amount of energy to remove four electrons leaving behind a carbon with six protons in its nucleus holding on just two electrons.

FOUR MARKS QUESTIONS

1. a) Write any two differences between saturated and unsaturated carbon compounds.

b) Write the structural formula of the following carbon compounds : i) Benzene ii) Butane (june 2022)

Ans. :

(Any two)

2. a) What are structural isomers ? Write the molecular and structural formula of butane.

b) What is catenation ? Write general formula for alkenes. (March 2022)

Ans. :

Carbon compounds having same molecular formula but different structural formulae
Molecular formula of butane is C4H10
Structural formula of butane is

Carbon has unique ability to form bonds with other atoms of carbon, giving rise to large molecules.
General formula for alkene is Cn H 2n

3. a) What are structural isomers ? Write two structures of butane molecule.

b) How would you distinguish experimentally between an alcohol and a carboxylic acid ? (Sep 2020)

Ans. :

Carbon compounds with identical molecular formula but different structures are called structural isomers.

b) Carboxylic acid reacts with carbonates and hydrogen carbonates to give rise to a salt, carbon dioxide and water. Alcohol will not react with carbonates and hydrogen carbonates.

4. a) How will ethanol be oxidised?

b) Explain the cleaning action of soaps. (April 2023)

Ans.:

a) Ethanol is oxidised into ethanoic acid by heating with oxidising agents like alkaline potassium permanganate or acidified potassium dichromate /

★ Soaps are sodium or potassium salts of long-chain carboxylic acids.

★ Soap molecules form micelles, in which the ionic end interacts with water and faces outside.

★ Carbon chain of the soap interacts with oil or dirt.

★ This forms emulsion in water. The soap molecules pull out the dirt and wash the clothes clean.

FIVE MARKS QUESTIONS

1. a) Write any two differences between saturated and unsaturated carbon compounds.

b) Write the molecular formula and structural formula for the following carbon compounds. i) propanoic acid ii) cyclohexane iii) pentane (KSEEB MQP 2021)

Ans: