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p -Block elements - ll — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryp -Block elements - ll1 Mark
MCQ
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 $A$
  • ✓
    $A$ is true but $R$ is false
✓

Answer

Correct option: D.
$A$ is true but $R$ is false
d
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.

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

So, assertion statement is correct but reason is incorrect.

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