JEE Main 2025 Jan 28 Shift 1, Chemistry Q24: Diazonium Salt

JEE Main2025Jan 28, Shift 1Chemistry

Consider the following sequence of reactions :

11.25 mg of chlorobenzene will produce _______ $\times 1 0^{- 1}$ mg of product B.

(Consider the reactions result in complete conversion.)

[Given molar mass of C, H, O, N and Cl as 12, 1, 16, 14 and 35.5 g mol $^{- 1}$ respectively]

Your answer

Solution

Identify the chain.

Step (i)+(ii): chlorobenzene $\to$ phenylmagnesium chloride $\to$ benzoic acid (PhCOOH) on quenching with CO $_{2}$ then H $_{3}$ O $^{+}$ .

Step (iii): PhCOOH + NH $_{3}$ on heating $\to$ benzamide PhCONH $_{2}$ (call this A).

Step Br $_{2}$ /NaOH: Hofmann bromamide degradation converts the amide into the corresponding amine with one fewer carbon. PhCONH $_{2} \to$ aniline PhNH $_{2}$ (product B).

Stoichiometry. One mole of chlorobenzene gives one mole of aniline.

$M (PhCl) = 6 (12) + 5 (1) + 35.5 = 112.5$ g mol $^{- 1}$
$M (PhNH_{2}) = 6 (12) + 7 (1) + 14 = 93$ g mol $^{- 1}$

Mass of aniline $= 11.25 mg \times \frac{93}{112.5} = 9.3$ mg.

Reported as $\times 1 0^{- 1}$ mg: $9.3 = 93 \times 1 0^{- 1}$ mg.

$∴$ Answer = $93$ .

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JEE Main 2025 Jan 28 Shift 1, Chemistry Q24: Diazonium Salt

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