Class X – Carbon and its Compounds

Ans. The second member of the alkyne family is propyne. Its structural formula is

CH₃ – C ≡ CH

Ans. (i) Self linking property called catenation

(ii) Carbon is tetravalent and can readily unite with atoms like hydrogen, oxygen etc. by electron sharing.

Ans. Carbon burns in oxygen or air to form gas. This reaction is highly exothermic that is why different form of coals are used as fuels.

Ans.

Ans.  Covalent bond is formed by sharing of electrons between two atoms. It is non-ionic in nature.

Ans. It is a cyclic compound with formula C₅H₁₀. The structure of the compound is represented as

Ethanal (CH₃CHO)

Butanone (CH₃COCH₂CH₃)

Ans. A series of similarly constituted compounds in which the members present have the same functional group, same chemical properties and any two successive members is a particular series differ in their molecular formula by CH₂ group.

(i) Same functional group

(ii) Same chemical properties

Pentane (C₅H₁₂)

Ans. No of isomers (alkane) = 2^{n – 4} + 1 (where n = no. of carbon)

No of isomers of pentane = 2^{5 – 4} + 1 = 2¹ + 1 = 3

Ans. Carbon atoms have 4 electrons in their outermost shell. So needs to gain or lose electrons to attain noble gas configuration. It could gain four electrons forming C^4- anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons.

It could lose four electrons forming C⁴⁺ cation. But it would require a large amount of energy to remove four electrons from its outermost shell. Because of these reasons, carbon shares its valence electrons to complete its octet with other atoms to form covalent bonds.

(i) Covalent compounds are bad conductors of electricity because they do not contain ions.

(ii) Covalent compounds have usually low melting and boiling point because they are made up of electronically neutral molecules. So the force of attraction between the molecules of a covalent compound is very weak. Only a small amount of heat energy is required to break these weak molecular forces, due to which covalent compounds have low melting and boiling points.

Ans. (a) Carbon forms carbon tetrachloride (CCl₄) with chlorine. Carbon (C) exhibits tetra-valency and form four covalent bonds with other elements. Chlorine atoms contains 7 valence electrons and forms covalent bond with other elements. The compound that is formed by the combination of carbon and chlorine is carbon tetrachloride.

(b) Carbon forms carbon dioxide (CO₂) with oxygen. Oxygen can form two covalent bonds and form carbon dioxide with carbon atom. The center carbon atom is bonded with two oxygen atoms through double covalent bonds. Hence the structure of carbon dioxide would be

O = = C = = O

Catenation is the ability of an atom to form bonds with other atoms of the same element. It is exhibited by both carbon and silicon. Carbon exhibits catenation much more than silicon in-fact no other element exhibits the property of catenation to the extent seen in carbon compounds.

Silicon forms compounds with hydrogen which have chains of upto seven or eight atoms, but these compounds are very reactive. The carbon – carbon bond is very strong and hence stable. This gives us the large number of compounds with many carbon atoms linked to each other.

CH₃ – CH₂ – CH₂ – CH₂ – CH₂ – CHO