Easy MCQ +4 / -1 PYQ · JEE Mains 2023

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: Butan -1- ol has higher boiling point than ethoxyethane.

Reason R: Extensive hydrogen bonding leads to stronger association of molecules.

In the light of the above statements, choose the correct answer from the options given below:

  1. A A is false but R is true
  2. B Both A and R are true but R is not the correct explanation of A
  3. C Both A and R are true and R is the correct explanation of A Correct answer
  4. D A is true but R is false

Solution

<p>The boiling point of a substance is dependent on the strength of the intermolecular forces between its molecules. Stronger intermolecular forces require more energy to overcome, thus resulting in a higher boiling point.</p> <p>In the case of butan-1-ol and ethoxyethane (diethyl ether), they are both composed of similar numbers of similar atoms, but the type of intermolecular force between the molecules differs due to their functional groups.</p> <p>Butan-1-ol is an alcohol and has a -OH group, which allows for hydrogen bonding, a strong type of dipole-dipole interaction. This happens when the hydrogen atom in a polar bond (especially -OH, -NH, -HF) is attracted to some electronegative atom (like O, N, or F) in another molecule. Because of this, butan-1-ol molecules &quot;stick together&quot; more strongly, requiring more heat energy to separate them and thus exhibiting a higher boiling point.</p> <p>On the other hand, ethoxyethane, being an ether, does not have the ability to form hydrogen bonds since it lacks the -OH group. The primary intermolecular forces in ethers are relatively weaker van der Waals forces. Therefore, it requires less heat energy to break these forces, resulting in a lower boiling point compared to butan-1-ol.</p> <p>So, both A and R are true and R is indeed the correct explanation for A.</p>

About this question

Subject: Chemistry · Chapter: Alcohols, Phenols and Ethers · Topic: Preparation and Properties of Alcohols

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