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CBSE Class 10 Science 2020 Outside Delhi Set 2

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Question : 5 of 7
Marks: +1, -0
(a) Carry out following conversions :
(i) Ethanol to Ethene
(ii) Ethanol to Ethanoic acid
(b) Differentiate between addition reaction and substitution reaction. Give one example of each.
Solution:  
(a) (i) Conversion of ethanol to ethene: Heating ethanol at 443K443 \mathrm{K} with excess concentrated sulphuric acid results in the dehydration of ethanol to give ethene.
CH3−CH2OHEthanol→H2SO4 Hot conc. CH2=CH2Ethene+H2O\underset{\text{Ethanol}}{\mathrm{CH}_3-\mathrm{CH}_2\mathrm{OH}} \xrightarrow[\mathrm{H}_2\mathrm{SO}_4]{\ \text{Hot conc.}\ } \underset{\text{Ethene}}{\mathrm{CH}_2=\mathrm{CH}_2} + \mathrm{H}_2\mathrm{O}
The concentrated sulphuric acid can be regarded as a dehydrating agent which removes water from ethanol.
(ii) Conversion of ethanol to ethanoic acid:
Ethanol can be converted to ethanoic acid in the presence of alkaline KMnO4\mathrm{KMnO}_4 and by heating the solution to give the ethanoic acid.
CH3−CH2OHEthanol  →Or acidified   K2Cr2O7+   Heat    Alkaline   KMnO4+HeatCH3COOHEthanoic acid\underset{\text{Ethanol}}{\mathrm{CH}_3-\mathrm{CH}_2\mathrm{OH}} \;\xrightarrow[\text{Or acidified } \;\mathrm{K}_2\mathrm{Cr}_2\mathrm{O}_7+ \;\text{ Heat }]{\;\text{ Alkaline }\;\mathrm{KMnO}_4 + \text{Heat}} \underset{\text{Ethanoic acid}}{\mathrm{CH}_3\mathrm{COOH}}
(b) Difference between addition and substitution reaction :
 S.No  Addition reaction  Substitution reaction
 1  It is the combination of two or more atoms or molecules in order to form a large molecule.  The large molecules formed after the reaction is called the adduct.
 2  The large molecules formed after the reaction is called the adduct.  The leaving group or the molecular components which leave the reaction and are being replaced are called substrates.
 3  No by-product is formed.  A by-product is formed.
Example of addition reaction :
Addition reaction is commonly used in the hydrogenation of vegetable oils using a nickel catalyst. Vegetable oils generally have long unsaturated carbon chains while animal fats have saturated carbon chains.
Example of substitution reaction:
In the presence of sunlight, chlorine is added to hydrocarbons in a very fast reaction. Chlorine can replace the hydrogen atoms one by one. Thus these reactions are used in the synthesis of the intermediates.
CH4+Cl2→ (in the presence of sunlight) CH3Cl+HCl\mathrm{CH}_4 + \mathrm{Cl}_2 \xrightarrow{\ \text{(in the presence of sunlight)}\ } \mathrm{CH}_3\mathrm{Cl} + \mathrm{HCl}
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