CBSE Class 10 Science Carbon and its Compounds MCQs Set H

Question. Carbon forms four covalent bonds by sharing its four valence electrons with four univalent atoms, e.g. hydrogen. After the formation of four bonds, carbon attains the electronic configuration of
(a) helium
(b) neon
(c) argon
(d) krypton 
Answer: b

Question. The correct electron dot structure of a water molecule is :
(a) H O H
(b) H O H
(c) H O H
(d) H O H
Answer: c

Question. Which of the following is not observed in a homologous series?
(a) Change in chemical properties
(b) Difference in —CH₂ and 14u molecular mass
(c) Gradation in physical properties
(d) Same functional group
Answer: a

Question. A molecule of ammonia (NH₃) has :
(a) only single bonds
(b) only double bonds
(c) only triple bonds
Answer: a

Question. Which of the following statements are usually correct for carbon compounds?
(i) These are good conductors of electricity.
(ii) These are poor conductors of electricity.
(iii) These have strong forces of attraction between their molecules.
(iv) These do not have strong forces of attraction between their molecules.
(a) (i) and (iii) (b) (ii) and (iii)
(c) (i) and (iv) (d) (ii) and (iv) 
(d) two double bonds and one single bond 
Answer: d

Question. Which of the following does not belong to the same homologous series?
(a) CH₄
(b) C₂H₆
(c) C₃H₈
(d) C₄H₈
Answer: d

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

Assertion and Reason Based MCQs

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is NOT the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is true.

Question. Assertion (A): Most of the carbon compounds are good conductors of electricity.
Reason (R): They do not dissociate to form ions and remain as molecules.
Answer: d

Question. Assertion (A): Following are the members of a homologous series : CH₃OH, CH₃CH₂OH, CH₃CH₂CH₂OH
Reason (R): A series of compounds with same functional group but differing by ––CH2 – unit is called a homologous series.
Answer: a

Question. Assertion (A): In a homologous series of alcohols, the formula for the second member is C₂H₅OH and the third member is C₃H₇OH.
Reason (R): The difference between the molecular masses of the two consecutive members of a homologous series is 144.
Answer: c

Question. Assertion (A): Carbon atoms have the ability to form four strong covalent bonds.
Reason (R): Carbon has the ability to make single, double and triple bonds with itself.
Answer: b

Question. Assertion (A): Third member of alkane is propane (C₃H₈)
Reason (R): It is obtained from general formula C_nH_{2n + 2}
Answer: a

Very Short Answer Type Questions :

 Question. What is a homologous series of carbon compounds ?
Answer: A homologous series is the family of organic compound having the same functional group, and the successive (adjacent) members of which differ by CH₂ unit or 14 atomic mass unit.

Question. Which element exhibits the property of catenation to maximum extent and why ?
Answer: Carbon, due to strong C—C bond.

Question. Name the process of converting vegetable oil to vegetable ghee.
OR
Name the process by which unsaturated fats gets changed to saturated fats.
Answer: Hydrogenation.

Question. Write the molecular formula of the 2nd and 3rd member of the homologous series whose first member is ethene. 
Answer: C₃H₆ and C₄H₈

Question. Name a cyclic unsaturated carbon compound.
Answer: Benzene.

 Question. Write the molecular formula of the 2nd and the 3rd member of the homologous series whose first member is methane. 
Answer: Ethane (C₂H₆)
Propane (C₃H₈)

Question. Write the molecular formula of first two members of homologous series having functional group -Br. U
Answer: CH₃Br, C₂H₅Br

Question. Name the functional group present in propanone.
Answer: Ketone.

Question. Write the number of covalent bonds in the molecule of ethane.
Answer: Seven covalent bonds.

Question. Write the next homologue of each of the following:
(i) C₂H₄ (ii) C₄H₆
Answer: (i) C₃H₆ (ii) C₅H₈

Question. How are covalent bonds formed ?
Answer: Covalent bonds are formed by the sharing of electrons between the atoms.

Question. Write the name and formula of the 2nd member of homologous series having general formula C_nH_2n
Answer: Name: Propene
Formula: C₃H₆

Question. Define catenation.
Answer: The property of self-linking of atoms of an element through covalent bonds in order to form straight chain, branched chains or cyclic chains of different sizes is called catenation. 

Question. Write the molecular formula of first two members of homologous series having function group – Cl.
Answer: The molecular formula of first two consecutive members of this series is:
CH₃Cl (Chloromethane)
C₂H₅Cl (Chloroethane)

Question. Select saturated hydrocarbons from the followings:
C₃H₆ , C₅H₁₀ , C4H₁₀ , C₆H₁₄ , C₂H₄
Answer: C₄H₁₀; C₆H₁₄.

Question. Write the molecular formula of the 2nd member of the homologous series where the first member is ethyne. 
Answer: C₃H₄, C₄H₆

Short Answer Type Questions :

Question. Give reason why carbon can neither form C₄⁺ cations nor C₄^– anions, but forms covalent compounds. Also, state the reason to explain why covalent compounds are bad conductors of electricity and have low melting and boiling points? 
Answer: Carbon cannot form C₄⁺ cation because removal of 4 electrons 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.
Hence, carbon atoms share electrons forming covalent compounds. 
Covalent compounds do not form ions/ charged particles and therefore do not conduct electricity. 
Inter-molecular forces of attraction are weak, hence they have low melting and boiling points.

Question. (a) Why most of the carbon compounds are poor conductor of electricity ?
(b) Write the name and structure of a saturated compound in which the carbon atoms are arranged in a ring. Give the number of single bonds present in this compound.
Answer: (a) Carbon compounds form covalent bonds/ do not dissociate into ions/do not have charged particles (ions)/do not have free electrons.
(b) Cyclohexane 3
Total no. of single bonds = 18

Question. The number of carbon compounds is more than those formed by all other elements put together.
Justify the statement by giving two reasons.
Answer: (i) Due to self linking ability of carbon/catenation.
(ii) Since carbon has a valency of four it can form bonds with four other atoms of carbon or atoms of some other monovalent element.
(iii) Due to small size of carbon it forms very strong and (or) stable bonds with other elements.

Question. What is a homologous series of carbon compounds?
Give an example and list its three characteristics.
Answer: A series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a homologous series. 
Example: Alkane / Alkene / Alkyne / Alcohol or any other one correct example. 
Characteristics:
(i) They have same general formula.
(ii) They have same functional group.
(iii) The difference in the molecular mass of two successive member is 14u.
(iv) The difference in the molecular formula of two successive member is of CH₂ unit.
(v) They have similar chemical properties.

Question. Give a test that can be used to confirm the presence of carbon in a compound. With a valency of 4, how is carbon able to attain noble gas configuration in its compounds? 
Answer: When carbon compound is burnt in the presence of oxygen, a gas is evolved.
Gas evolved turns lime water milky.
By sharing its four valence electrons with other elements, carbon attains stable noble gas configuration.

Question. What are covalent compounds? How are they different from ionic compounds? List any two properties of covalent compounds.
Answer: The compounds that are formed due to sharing of electrons between two atoms/compounds having covalent bonds. 
Ionic compounds are formed due to transfer of electrons from one atom to another/compounds having ionic bonds/compounds having attraction between oppositely charged ions 
(i) They are poor conductors of electricity 
(ii) They have low melting and boiling point.

Long Answer Type Questions :

Question. Why are certain compounds called hydrocarbons ? Write the general formula for homologous series of alkanes, alkenes and alkynes and also draw the structure of the first member of each series. Write the name of the reaction that converts alkenes into alkanes and also write a chemical equation to show the necessary conditions for the reaction to occur.
Answer: The hydrocarbons are the compounds that consist of carbon and hydrogen.
The alkanes are known as the saturated hydrocarbons as they have compounds of carbon that are single bonded and has the general formula C_nH_2n+2
Alkenes are unsaturated hydrocarbons and are made up of compounds of carbon that are double bonded and has the general formula C_nH_2n.
Alkynes are also unsaturated hydrocarbons that are made up of compounds of carbon that are triple bonded and have a general formula C_nH_{2n – 2}
The structure of the first members of each series are as follows:
The hydrogenation reaction is a reaction that helps in converting unsaturated hydrocarbons to the saturated hydrocarbons. The conversion of alkenes to alkane is an example of hydrogenation reaction.