Write one chemical equation to represent each of the following types of reactions of organic substances:

(i) Esterification

(ii) Saponification

(iii) Substitution

Carbon and its Compounds

Chemical Properties of Carbon Compounds

Official Answer

The chemical equations representing the three types of organic reactions are:

(i) Esterification Reaction:

When ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst, a sweet-smelling substance called an ester (ethyl ethanoate) is formed:

$\text{CH}_3 ext{COOH} + \text{CH}_3 ext{CH}_2 ext{OH} \xrightarrow{\text{Acid}} \text{CH}_3 ext{COOCH}_2 ext{CH}_3 + \text{H}_2 ext{O}$

(ii) Saponification Reaction:

On treating an ester with an alkali like sodium hydroxide, it is converted back into alcohol and the sodium salt of the carboxylic acid. This reaction is used in the preparation of soap:

$\text{CH}_3 ext{COOCH}_2 ext{CH}_3 + \text{NaOH} \rightarrow \text{CH}_3 ext{COONa} + \text{CH}_3 ext{CH}_2 ext{OH}$

(iii) Substitution Reaction:

Saturated hydrocarbons undergo substitution reactions with chlorine in the presence of sunlight, where chlorine atoms replace hydrogen atoms one by one:

$\text{CH}_4 + \text{Cl}_2 \xrightarrow{\text{Sunlight}} \text{CH}_3 ext{Cl} + \text{HCl}$

EsterificationSaponificationSubstitutionethyl ethanoatesodium acetatechloromethanesunlight

Marking Scheme

1Correct chemical equation for Esterification with catalyst (1 mark)
2Correct chemical equation for Saponification (1 mark)
3Correct chemical equation for Substitution with sunlight condition (1 mark)

Hint

Remember that esterification requires an acid catalyst, saponification requires a strong base like $\text{NaOH}$ , and substitution of alkanes requires sunlight.

Quick Oral Answer

Esterification produces a sweet-smelling ester from an acid and an alcohol. Saponification breaks down an ester using a base to form soap and alcohol. Substitution replaces hydrogen in a saturated hydrocarbon with a halogen in the presence of sunlight.

Analysis & Explanation

Esterification is a condensation reaction between a carboxylic acid and an alcohol. Saponification is the base-catalyzed hydrolysis of that ester, which is the chemical basis for soap-making. Substitution reactions are characteristic of saturated hydrocarbons because they are generally unreactive but can undergo hydrogen replacement under energetic conditions like UV/sunlight.

Common Mistakes

1Forgetting to write reaction conditions like 'Acid' over the arrow in esterification or 'Sunlight' in substitution.
2Writing incorrect molecular formulas for ethyl ethanoate (often confusing the ethyl and methyl parts).

Interesting Facts

Esters are widely used in making perfumes and artificial flavoring agents due to their pleasant, fruity smell.

Saponification literally means 'soap-making' from the Latin word 'sapo'.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2011?

This question carries 3 marks in the CBSE Class 10 Science 2011 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Carbon and its Compounds" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Chemical Properties of Carbon Compounds" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2011 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2011 paper.