NEET · Chemistry · STD 12 - p -Block elements - ll

Given below are two statements : one is labelled as Assertion \(A\) and the other is labelled as Reason \(R:\) Assertion \(A:\) Metallic sodium dissolves in liquid ammonia giving a deep blue solution, which is paramagnetic. Reason \(R:\) 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 :

A \(A\) is false but \(R\) is true
B Both \(A\) and \(R\) are true and \(R\) is the correct explanation of \(A\)
C Both \(A\) and \(R\) are true but \(R\) is NOT the correct explanation of \(A\)
D \(A\) is true but \(R\) is false

Verified Solution

Answer & Solution

Correct Answer

(D) \(A\) is true but \(R\) is false

Step-by-step Solution

Detailed explanation

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. \(M +(x+y) NH _3 \rightarrow\left[ M \left( NH _3\right)\right]^{+}+\left[e\left( NH _3\right) y\right]^{-}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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