Question: Assertion (A) : Benzene diazonium salt is stable and can be easily stored. Reason (R) : Benzene diazonium chloride decomposes easily.

Step 1 (Conceptual Analysis of Assertion): [0.25 Mark]
The Assertion states that benzene diazonium salt is stable and can be stored. According to NCERT, benzene diazonium salts are highly unstable and reactive due to the presence of the diazonium group ($-N_2^+$), which is an excellent leaving group. They are typically prepared and used in situ at low temperatures ($273-278\text{ K}$). Therefore, the Assertion (A) is False.

Step 2 (Conceptual Analysis of Reason): [0.5 Mark]
The Reason states that benzene diazonium chloride decomposes easily. This is chemically accurate. The decomposition reaction is represented as:

Because the $N_2$ molecule is a very stable leaving group, the salt decomposes readily at room temperature. Therefore, the Reason (R) is True.

Step 3 (Final Concluded Answer): [0.25 Mark]
Based on the analysis, Assertion (A) is False, but Reason (R) is True. In the standard CBSE format, the correct option is: (d) Assertion (A) is false but Reason (R) is true.

💡 EL10 Concept Insight: Think of a benzene diazonium salt like a person holding a very hot potato (the $N_2$ gas); they want to drop it as fast as possible to be stable, which is why the salt falls apart (decomposes) almost immediately if you don't keep it in an ice-cold environment.