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Science · 2023 · 5 marks
CBSE 2023 · Region 5 · Set 3 · Q36
(a) Explain why carbon forms compounds mainly by covalent bonds. Explain in brief two main reasons for carbon forming a large number of compounds.…
Explain why carbon forms compounds mainly by covalent bonds. Explain in brief two main reasons for carbon forming a large number of compounds. Why does carbon form strong bonds with most other elements ?
(i)
Write the name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen can take place. Stating the essential condition required for an addition reaction to occur, write the chemical equation giving the name of the reactant and product of such a reaction. How is an addition reaction different from a substitution reaction ?
(ii)
Write the structure of benzene.
Marking-scheme solution
Carbon has $\displaystyle 4$ electrons in its outermost shell, and needs to gain or
lose $\displaystyle 4$ electrons to attain noble gas configuration.
Losing or gaining $\displaystyle 4$ electrons is not possible due to energy
considerations, hence it shares electrons to form covalent bonds.
Two reasons :
(i)
Catenation : Unique ability of carbon to form bonds with other atoms
of carbon, giving rise to long chains of different types of compounds.
(ii)
Tetravalency : Since carbon has a valiancy of $\displaystyle 4$, it is capable of
bonding with four other atoms of carbon or atoms of elements like
oxygen, hydrogen, nitrogen, sulphur, chlorine etc.
The reason for the formation of strong bonds by carbon is its small size
which enables the nucleus to hold on to the shared pair of electrons
strongly.
(i)
Alkene, $\displaystyle \mathrm{C}_{\mathrm{n}} \mathrm{H}_{2 \mathrm{n}} /$ Alkyne,$\displaystyle \mathrm{C}_{\mathrm{n}} \mathrm{H}_{2 \mathrm{n}-2}$
-Presence of catalyst such as Ni or Palladium
In addition reaction unsaturated hydrocarbon gets converted to
saturated hydro carbon whereas in substitution reaction one atom or a
group of atoms replace hydrogen in a saturated hydrocarbon.
(ii)
All Carbon and its Compounds questions2023 question paperNCERT solutions: Carbon and its CompoundsPractice Carbon and its Compounds →
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CBSE Class 10 Science past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.