Q30Written answer
Draw the electron dot structure of ethyne and also draw its structural formula
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Worked solution
Molecular formula= C2H2
Electronic Formula
Structural formula= H-C≡C-H
NCERT Exemplar · Class 10 · Science
Chapter 4: Carbon and Its Compounds
Practice each question, then open the answer or worked solution.
Short Answer Questions
23 questionsQ31Written answer
Write the names of the following compounds
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Worked solution
- Pentanoic acid
- Butyne
- Heptanal
- Pentanol
Q32Written answer
Identify and name the functional groups present in the following compounds.
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- Alcohol
- Carboxylic acid
- Ketone
- Alkene
Q33Written answer
A compound X is formed by the reaction of a carboxylic acid C2H4O2 and an alcohol in the presence of a few drops of H2SO4. The alcohol on oxidation with alkaline KMnO4 followed by acidification gives the same carboxylic acid as used in this reaction. Give the names and structures of (a) carboxylic acid, (b) alcohol and (c) the compound X. Also write the reaction.
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Worked solution
Carboxylic acid = CH3COOH ethanoic acid
Alcohol = CH3CH2OH ethanol
X = CH3COOCH2CH3 ethyl ethanoate
Q34Written answer
Why detergents are better cleansing agents than soaps? Explain.
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Worked solution
Detergents are better than soaps because detergents are ammonium or sulphonate salts of long-chain carboxylic acids. Charged ends of theses will not for precipitate with calcium and magnesium present in hard water. On the other hand, soaps will form a precipitate with calcium and magnesium ions present in the hard water.
Q35Written answer
Name the functional groups present in the following compounds
(a) CH3COCH2 CH2 CH2 CH3
(b) CH3CH2CH2COOH
(c) CH3CH2 CH2 CH2 CHO
(d) CH3CH2OH
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Worked solution
- Ketone
- Carboxylic acid
- Aldehyde
- Alcohol
Q36Written answer
How is ethene prepared from ethanol? Give the reaction involved in it.
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Ethanol is heated at 443k along with excess Sulphuric acid to obtain Ethene.
CH3-CH2OH ——->CH2=CH2 +H2O
(ethanol) (H2SO4) (ethene)
Q37Written answer
Intake of a small quantity of methanol can be lethal. Comment.
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Worked solution
Methanol gets converted to Methanal and liver and kills all the cells. Methanol also affects the optic nerves and causes blindness. Hence intake of a small quantity of methanol can be lethal.
Q38Written answer
A gas is evolved when ethanol reacts with sodium. Name the gas evolved and also write the balanced chemical equation of the reaction involved.
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Worked solution
When ethanol reacts with sodium it gives Sodium ethoxide with the liberation of hydrogen gas.
2CH₃- CH₂-OH +2Na——>2 CH₃- CH₂- ONa + H₂
Q39Written answer
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.
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Worked solution
Sulphuric acid acts as a catalyst and a dehydrating agent in the formation of ethene.
