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Science · 2026 · 4 marks
CBSE 2026 · Region 5 · Set 1 · Q28
Alcohol forms a homologous series with general formula C_n H_2 n +1 - OH and -OH group as functional group. Ethanol is commonly called alcohol and is…
Alcohol forms a homologous series with general formula $\displaystyle \mathrm{C}_{\mathrm{n}} \mathrm{H}_{2 \mathrm{n}+1}-\mathrm{OH}$ and -OH group as functional group. Ethanol is commonly called alcohol and is used in alcoholic drinks. It is good solvent, used in medicines, cough syrups, tonics etc. $\displaystyle 1$+$\displaystyle 1$+$\displaystyle 2$
(a)
Write structural formula and name of $\displaystyle 4^{\text {th }}$ member of alcohol homologous series.
(b)
What happens when ethanol is heated with alkaline $\displaystyle \mathrm{KMnO}_{4}$ ? Write chemical equation involved.
(c)
Write the chemical equation of reaction of ethanol with ethanoic acid in the presence of concentrated $\displaystyle \mathrm{H}_{2} \mathrm{SO}_{4}$. Write the name of this reaction.
OR
(c)
What happens when ethanol is heated with excess concentrated sulphuric acid at $\displaystyle 443$ K ? Write chemical equation involved. What is the role of concentrated sulphuric acid in this reaction ?
Marking-scheme solution
(a)
$\displaystyle \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{OH}$
Butanol
(b)
Ethanol gets oxidised to form ethanoic acid.
$\displaystyle \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{OH} \xrightarrow{\text { alkaline } \mathrm{KMnO}_{4}+\text { heat }} \mathrm{CH}_{3} \mathrm{COOH}$
Esterification reaction.
Ethanol will get dehydrated to form ethene.
$\displaystyle \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} \xrightarrow{\text { Conc. } \mathrm{H}_{2} \mathrm{SO}_{4} \text { at } 443 \mathrm{~K}} \mathrm{CH}_{2}=\mathrm{CH}_{2}+\mathrm{H}_{2} \mathrm{O}$
Dehydrating agent/ Catalyst
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CBSE Class 10 Science past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.