Carbon and Its Compounds
Exemplar Problems Short Answer II
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
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)
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.
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.
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)
Write the structural formulae of all the isomers of hexane.
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.