Class X – Carbon and its Compounds (PYQs) – Solutions

Ans. It has 3 bonds around N-atom.

Ans. It is because covalent compounds do not form ions.

4. Explain why carbon generally forms compounds by covalent bonds or do not form ionic compounds.

OR

Give reason why carbon neither forms C⁴⁺ cations nor C^4– anions but form covalent compounds which are bad conductors of electricity and have low melting and boiling points.

OR

Carbon has four electrons in its valence shell. How does carbon attain stable configuration?

Ans. Carbon since it forms strong covalent bond, due to smaller atomic size.

Ans. Carbon compounds form covalent bonds/do not dissociate into ions/do not have charged particles (ions).

Ans. 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.

Ans. It is because they have weak van der Waal’s forces of attraction between molecules therefore have low melting and boiling points.

Ans. Covalent bonds are formed by equal sharing of electrons.

Ans. – Burn compound in air/ oxygen; Gas evolved turns lime water milky

– By sharing its four valence electrons with other elements.

– Due to self-linking ability of carbon/catenation

– Since carbon has a valency of four it can form bonds with four other atoms of carbon or atoms of some other mono-valent element.

– Due to small size of carbon it forms very strong and (or) stable bonds with other elements

Ans. Those compounds which are formed by equal sharing of electrons are called covalent compounds. They are different from ionic compounds since ionic compounds are formed by transfer of electrons from one atom to another.

Properties:

(i) They have low melting and boiling points.

(ii) They do not conduct electricity in molten state and in aqueous solution.

(iii) They are mostly insoluble in water but soluble in organic solvents except glucose, sugar, urea, ethyl alcohol, etc.

Ans. Carbon has electronic configuration 2, 4. It could gain four electrons forming C-4 anion or lose 4 electrons to form C+4 cation. Both are not possible due to energy considerations. Carbon overcome this problem by sharing electrons and forming covalent compounds. Two reasons for forming large number of compounds:

(1) Catenation (2) Tetra valency

Ans. Formation of NH3 molecule Three hydrogen atoms each share their 1 electron with nitrogen to form three covalent bonds and make an ammonia molecule (NH₃).

Ans. Carbon shows the property of catenation. It forms strong covalent bonds with other atoms of carbon forming long straight, branched and closed chain compounds.

Carbon is smallest in size in group 14 with tatravalency, it can form double as well as triple bonds, therefore, it can show property of catenation to maximum extent and forms 3 million compounds other elements cannot show property of catenation to this extent due to larger size form weaker covalent bond and cannot form double or triple bonds.

Ans.

Ans. Ionic compounds do not conduct in solid state due to absence of free ions but they conduct electricity in molten and aqueous state due to presence of free ions.

Ans. C₆H₆. It has three double bonds

Ans. It is a series of organic compounds having same functional group and similar chemical properties.

Ans. C_nH_2n, Ethene is simplest alkene.

(i) C₃H₆, (ii) C₅H₈

Ans. C₄H₉OH or CH₃CH₂CH₂CH₂OH (Butan-1-ol)

Ans. C₂H₆, Ethane

Ans. C₃H₄, Propyne

Ans. Carboxylic acid

Ans. ‘A’ belongs to Alkynes, ‘B’ belongs to Alkenes.

Ans. The general formula of the compounds having –Cl functional group is C_nH_{2n + 1}Cl. Its two members are:

(i) CH₃Cl (ii) CH₃ – CH₂ – Cl

Ans. (i) CH₃CH₃ (Ethane); where n is 2

(ii) CH₃CH₂CH₃ (Propane); where n is 3

Ans. There are 7 covalent bonds.

Ans. There are 10 covalent bonds.

Ans. There are 13 covalent bonds.

Ans. Benzene is cyclic unsaturated carbon compound.

Ans. It does not occur due to the presence of the same functional group.

Ans. Unsaturated hydrocarbons with double bonds.

Ans. ‘C’ has minimum boiling point, so ‘C’ has minimum no. of C-atoms.

Ans. Alkene

C₂H₄ and C₄H₈ are alkenes, C₃H₄ and C₂H₂ are alkynes.

Ans. The series of organic compounds having same functional group and similar chemical properties is called homologous series. For example,

Characteristics:

• Each successive member differs by CH₂ unit.
• They have gradation in physical properties.
• They have similar chemical properties due to presence of same functional group.