Chemistry · Alkali Metals - Group 1

NEET (UG) 2023 — Question 181

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason $\mathbf{R}$ :

Assertion A : Metallic sodium dissolves in liquid ammonia giving a deep blue solution, which is paramagnetic.

Reason $\mathbf{R}$ : The deep blue solution is due to the formation of amide.

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

Option A:
Both A and R are true but R is NOT the correct explanation of A
Option B:
A is true but R is false
Correct
Option C:
A is false but R is true
Option D:
Both A and R are true and R is the correct explanation of A

Answer: B

Step-by-step solution

On dissolving alkali metal (sodium) in liquid ammonia, a deep blue solution is developed due to

ammoniated electron which absorbs energy in visible region of light and imparts blue colour.

Due to unpaired electron, solution is paramagnetic. $\mathrm{M}+(\mathrm{x}+\mathrm{y}) \mathrm{NH}_3\rightarrow\left[\mathrm{M}\left(\mathrm{NH}_3\right)_{\mathrm{x}}\right]^{+}+\left[\mathrm{e}\left(\mathrm{NH}_3\right) \mathrm{y}\right]^{-}$

So, assertion statement is correct but reason is incorrect.

Answer key and solution verified before publishing.

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Exam: NEET (UG) 2023
Paper: 2023 paper
Subject: Chemistry
Chapter: Alkali Metals - Group 1
Topic: Introduction & Properties of Group 1 metals