Consider the following reaction sequence in which J, K, L and M are the major products.

Given:
Atomic mass (in amu): H : 1, C : 12, N : 14, O : 16, S : 32, Br : 80, Ba : 137

In sulphur estimation by Carius method, the amount of BaSO₄ formed from 3.79 g of M is _______ g.

The correct answer is 2.33.

Step 1: Understand the reaction sequence to identify compounds J, K, and M.

Starting reactant: m-xylene (1,3-dimethylbenzene).

1. Formation of J:
- m-Xylene undergoes Friedel-Crafts acylation with chloroacetyl chloride ($''Cl-CO-CH''$₂Cl) in the presence of anhydrous $''AlCl''$₃. Electro-substitution takes place at the position ortho/para to both methyl groups (position 4 of 1,3-dimethylbenzene), forming 2-chloro-1-(2,4-dimethylphenyl)ethan-1-one.
- Treatment with $''NaI''$ under heat converts the $''-Cl''$ group into an $''-I''$ group via Finkelstein reaction.
- Reaction with sodium 3-nitrophenoxide ($''NaO-C''$₆$''H''$₄-NO₂) replaces iodine through an S_N2 substitution, yielding ketone compound J.

2. Formation of K:
- Reduction of ketone J using $''NaBH''$₄ yields the corresponding secondary alcohol.
- Treatment with $''PBr''$₃ replaces the alcohol group ($''-OH''$) with a bromine atom ($''-Br''$), giving compound K.
- Molecular structure of K: $''C''$₁₆H₁₆BrNO₃.
- Molar mass of K = $''(16\; \times \; 12)\; +\; (16\; \times \; 1)\; +\; 80\; +\; 14\; +\; (3\; \times \; 16)\; =\; 192\; +\; 16\; +\; 80\; +\; 14\; +\; 48\; =\; 350\; g/mol''$, which matches the given molar mass in the image.

3. Formation of M:
- Compound K reacts with sodium thiophenolate ($''PhSNa''$) via an S_N2 nucleophilic substitution, replacing the $''-Br''$ atom with a phenylthio group ($''-SPh''$) to give compound M.
- Structure of M: $''C''$₂₂H₂₁NO₃S.

Step 2: Calculate the Molar Mass of Compound M

Molecular formula of M = $''C''$₂₂H₂₁NO₃S
Using given atomic masses: $''H\; =\; 1,\; C\; =\; 12,\; N\; =\; 14,\; O\; =\; 16,\; S\; =\; 32''$

$''Molar\; mass\; of\; M''=(22\times 12)+(21\times 1)+14+(3\times 16)+32$

$''Molar\; mass\; of\; M''=264+21+14+48+32=379\text{ g/mol}$

Step 3: Carius Method Principle for Sulphur Estimation

In the Carius method, all sulphur present in compound M is quantitatively converted into barium sulphate ($''BaSO''$₄).

By Principle of Atom Conservation (POAC) on Sulphur atoms:
Moles of $''S''$ in compound M = Moles of $''BaSO''$₄ formed

Since 1 mole of compound M contains 1 mole of sulphur ($''S''$):
Moles of M = Moles of $''BaSO''$₄

Step 4: Molar Mass of Barium Sulphate ($''BaSO''$₄)

$''Molar\; mass\; of\; BaSO''$₄ = 137+32+(4×16) = 137+32+64 = 233 g/mol

Step 5: Calculate Mass of $''BaSO''$₄ Formed

Given mass of compound M = $3.79\text{ g}$

$''Moles\; of\; M''=\frac{3.79}{379}=0.01\text{ mol}$

$''Moles\; of\; BaSO''$₄ = Moles of M = 0.01 mol

$''Amount\; of\; BaSO''$₄ formed = Moles of BaSO₄ × Molar mass of BaSO₄

$''Amount\; of\; BaSO''$₄ formed = 0.01 × 233 = 2.33 g

Thus, the amount of $''BaSO''$₄ formed is 2.33 g.