Q13
1 markMCQSection A

Assertion (A): Following are the members of a homologous series: CH3OH,CH3CH2OH,CH3CH2CH2OH\text{CH}_3\text{OH}, \text{CH}_3\text{CH}_2\text{OH}, \text{CH}_3\text{CH}_2\text{CH}_2\text{OH}

Reason (R): A series of compounds with same functional group but differing by −CH2−-\text{CH}_2- unit is called a homologous series.

Carbon and its Compounds
Versatile Nature of Carbon

Options

(0)Both (A) and (R) are true and (R) is correct explanation of the assertion.
(1)Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
(2)(A) is true but (R) is false.
(3)(A) is false but (R) is true.
Official Answer

Both (A) and (R) are true and (R) is correct explanation of the assertion.

homologous seriesfunctional group−CH2−-\text{CH}_2- unitdifference

Marking Scheme

  • 1Identifying that both Assertion and Reason are correct statements (0.5 marks)
  • 2Establishing that the Reason is the correct explanation for the Assertion (0.5 marks)

Hint

Check if the given compounds have the same functional group and if their successive molecular formulas differ by a −CH2−-\text{CH}_2- unit.

Quick Oral Answer

A homologous series is a family of organic compounds with the same functional group where successive members differ by a −CH2−-\text{CH}_2- unit. Methanol, ethanol, and propanol are classic examples of the alcohol homologous series.

Analysis & Explanation

The Assertion (A) states that CH3OH\text{CH}_3\text{OH} (methanol), CH3CH2OH\text{CH}_3\text{CH}_2\text{OH} (ethanol), and CH3CH2CH2OH\text{CH}_3\text{CH}_2\text{CH}_2\text{OH} (propanol) are members of a homologous series. This is true because they all contain the same functional group (−OH-\text{OH}, alcohol) and successive members differ by a −CH2−-\text{CH}_2- unit. The Reason (R) correctly defines a homologous series as a series of compounds with the same functional group but differing by a −CH2−-\text{CH}_2- unit. Since the reason directly explains why the given compounds form a homologous series, (R) is the correct explanation of (A).

Common Mistakes

  1. 1Students sometimes fail to verify if the difference between successive members is exactly −CH2−-\text{CH}_2-.
  2. 2Confusing homologous series with structural isomers.

Interesting Facts

As the molecular mass increases in any homologous series, a gradual gradation in physical properties (like melting and boiling points) is observed.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2020?

This question carries 1 mark in the CBSE Class 10 Science 2020 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 "Versatile Nature of Carbon" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2020 paper?

This is a MCQ question from Section A in the CBSE Class 10 Science 2020 paper.