. Number of different $\text{H}$-atoms in $(\text{Y})$
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Hinsberg's test differentiates primary, secondary, and tertiary amines based on the nature of the sulfonamide product: $1^\circ$ amine product is soluble in base, $2^\circ$ amine product is insoluble, and $3^\circ$ amine does not react. Counting unique $\text{H}$ environments requires analyzing chemical equivalence and symmetry.
Step 1: Aniline reacts with $CHCl_3/KOH$ to give phenyl isocyanide (carbylamine reaction), which has foul smell.
Step 2: Aniline reacts with benzene sulphonyl chloride to form sulphonamide (Hinsberg reaction):
\[
Ph-NH_2 + Ph-SO_2Cl \rightarrow Ph-SO_2-NH-Ph
\]
Step 3: This sulphonamide has acidic N–H proton and dissolves in $NaOH$ forming soluble salt.
Step 4: Structure of $Y = Ph-SO_2-NH-Ph$.
Step 5: Different hydrogen environments:
\begin{itemize}
\item One N–H hydrogen
\item Three types (ortho, meta, para) on first phenyl ring
\item Three types (ortho, meta, para) on second phenyl ring
\end{itemize}
Step 6: Total different hydrogens $= 1+3+3=7$.
Hence, correct answer is 7.
