Carbon and Its Compounds NCERT Exemplar Problems

Short Answer II

Question 10: Ethene is formed when ethanol at 443 K is heated with excess of concentrated sulphuric acid. What is the role of sulphuric acid in this reaction? Write the balanced chemical equation of this reaction.

Answer: In this reaction, sulphuric acid is working as a dehydrating agent.

CH₃CH₂OH + hot conc. H₂SO₄ at 443 K → H₂C=CH₂ + H₂

Question 11: Carbon, Group (14) element in the Periodic Table, is known to form compounds with many elements. Write an example of a compound formed with

chlorine (Group 17 of Periodic Table)

Answer: Carbon tetrachloride (CCl₄)
oxygen (Group 16 of Periodic Table)

Answer: Carbon dioxide (CO₂)

Question 12: 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. Compare the ability of catenation of the two elements. Give reasons.

Answer: Both carbon and silicon show the ability for catenation. But carbon shows a better ability to do so; compared to silicon or any other element. This is possible because the carbon atom is smaller in size than the silicon atom. Long chain compounds of silicon are not as stable as those of carbon.

Question 13: Unsaturated hydrocarbons contain multiple bonds between the two C-atoms and show addition reactions. Give the test to distinguish ethane from ethene.

Answer: Combustion is very good test to differentiate between saturated and unsaturated hydrocarbons. A saturated hydrocarbon undergoes complete combustion and hence burns with blue flame. It does not leave any residue after burning. On the other hand, unsaturated hydrocarbon undergoes incomplete combustion and hence burns with yellow flames and leaves some residue. Ethane; being a saturated hydrocarbon; burns with a blue flame and does not leave residue. Ethene; being an unsaturated hydrocarbon; burns with a yellow flame and leaves some residue.

Question 14: Match the reactions given in Column (A) with the names given in column (B)

Column A	Column B
(a) CH₃OH + CH₃COOH + H⁺ → CH₃COOCH₃ + H₂O	(i) Addition reaction
(b) CH₂=CH₂ + H₂ + Ni → CH₂-CH₃	(ii) Substitution reaction
(c) CH₄ + Cl₂ + sunlight →CH₃Cl + HCl	(iii) Neutralization reaction
(d) CH₃COOH + NaOH →CH₃COONa + H₂O	(iv) Esterificaion reaction

Answer: (a) → (iv), (b) → (i), (c) → (ii), (d) → (iii)

Question 15: Write the structural formulae of all the isomers of hexane.

Answer:

Question 16: What is the role of metal or reagents written in small brackets in the given chemical reactions?

H₆C₃=C₃H₆ + (Ni) → C₆H₁₄

Answer: Nickel is working as catalyst
CH₃COOH +CH₃CH₂OH + (conc.H₂SO₄)→ CH₃COOC₂H₅ + H₂O

Answer: Sulphuric acid is working as catalyst
CH₃CH₂OH + (alk.KMnO₄) → CH₃COOH

Answer: Potassium permanganate is working as oxidising agent.