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Science · 2024 · 5 marks
CBSE 2024 · Region 1 · Set 1 · Q34
(i)Define a homologous series of carbon compounds.(ii)Why is the melting and boiling points of $\displaystyle \mathrm{C}_{4} \mathrm{H}_{8}$ higher than that of $\displaystyle \mathrm{C}_{3} \mathrm{H}_{6}$ or $\displaystyle \mathrm{C}_{2} \mathrm{H}_{4}$ ?(iii)Why do we NOT see any gradation in chemical properties of a homologous series compounds ?(iv)Write the name and structures of (i) aldehyde and (ii) ketone with molecular form $\displaystyle \mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$.(i)Write the name and structure of an organic compound 'X' having two carbon atoms in its molecule and its name is suffixed with '-ol'.(ii)What happens when 'X' is heated with excess concentrated sulphuric acid at $\displaystyle 443$ K? Write chemical equation for the reaction stating the conditions for the reaction. Also state the role played by concentrated sulphuric acid in the reaction.(iii)Name and draw the electron dot structure of hydrocarbon produced in the above reaction.
(i)
Define a homologous series of carbon compounds.
(ii)
Why is the melting and boiling points of $\displaystyle \mathrm{C}_{4} \mathrm{H}_{8}$ higher than that of $\displaystyle \mathrm{C}_{3} \mathrm{H}_{6}$ or $\displaystyle \mathrm{C}_{2} \mathrm{H}_{4}$ ?
(iii)
Why do we NOT see any gradation in chemical properties of a homologous series compounds ?
(iv)
Write the name and structures of (i) aldehyde and (ii) ketone with molecular form $\displaystyle \mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$.
(i)
Write the name and structure of an organic compound 'X' having two carbon atoms in its molecule and its name is suffixed with '-ol'.
(ii)
What happens when 'X' is heated with excess concentrated sulphuric acid at $\displaystyle 443$ K? Write chemical equation for the reaction stating the conditions for the reaction. Also state the role played by concentrated sulphuric acid in the reaction.
(iii)
Name and draw the electron dot structure of hydrocarbon produced in the above reaction.
Marking-scheme solution
(i)
A series of carbon compounds in which the same functional group
substitutes for hydrogen in a carbon chain / Series of compounds having
same functional group and similar chemical properties.
(ii)
Because melting point and boiling point increase with molecular
mass.
(iii)
Because chemical properties of organic compounds are solely
determined by their functional group which remains same in a
homologous series.
(iv)
(i)
Aldehyde: Propanal
(ii)
Ketone: Propanone
(i)
Ethanol
Structure:
(ii)
Ethene is formed
Concentrated Sulphuric acid acts as a dehydrating agent.
(iii)
Ethene
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CBSE Class 10 Science past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.