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Carbon and its Compounds — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceCarbon and its Compounds5 Marks
Question
  1. Why does carbon form compounds mainly by covalent bonding?
  2. List any two reasons for carbon forming a very large number of compounds.
  3. An organic acid ‘X’ is a liquid which often freezes during winter time in cold countries, has the molecular formula, $C _2 H _4 O _2$ On warming it with ethanol in the presence of a few drops of concentrated sulphuric acid, a compound ‘Y’ with a sweet smell is formed.
  1. Identify ‘X’ and ‘Y’.
  2. Write a chemical equation for the reaction involved.
✓

Answer

  1. Carbon has 4 electrons in its valence shell. To attain stability, it should either gain 4 electrons or lose 4 electrons. It cannot lose 4 electrons as it involves a lot of energy. Also, it cannot gain 4 electrons because the nucleus cannot hold on to the four extra electrons added. Therefore, to complete the octet, it shares 4 electrons with other atoms. That is why, carbon forms compounds mainly by covalent bonding.
  2. Reasons for carbon forming a very large number of compounds:
  1. Catenation: The unique ability of carbon to form bonds with other atoms of carbon giving rise to long chains of different types of compounds.
  2. Isomerism: Ability of carbon to form compounds with same molecular formula but different structures.
  3. Tetravalency: Since carbon has a valency of 4, it is capable of bonding with four other atoms of carbon or atoms of elements like oxygen, hydrogen, nitrogen, sulphur, chlorine, etc.
  4. The bonds formed by carbon with other elements are very strong because of its small size which enables the nucleus to hold on to the shared pairs of electrons strongly.
  1.  
  1. $\text{X}: \text{Ethanoic acid/}\text{CH}_{3}\text{COOH}$
$\text{Y}: \text{CH}_{3}\text{COOC}_{2}\text{H}_{5}/\text{Ethyl Acetate/Ethyl Ethanoate}$
  1. $\text{CH}_{3}\text{COOH} + \text{C}_{2}\text{H}_{5}\text{OH}\xrightarrow[]{\text{conc. H}_{2}\text{SO}_{4}}\text{CH}_{3}\text{COOC}_{2}\text{H}_{5} + \text{H}_{2}\text{O}$

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