Verified Solution • 2025–26 Session moderate

QJEEM21Ch608a: JEE Main 2021 Chemistry - Class 12 JEEM21Ch608a Solution: 1.22 g of an organic acid is separately dissolved in 100 g of…

1.22 g of an organic acid is separately dissolved in 100 g of benzene (Kb = 2.6 K kg mol −- 1) and 100 g of acetone (Kb = 1.7 K kg mol −- 1). The acid is known to dimerize in benzene but remain as a monomer in acetone. The boiling point of the solution in acetone increases by 0.17 ∘^\circ C. The increase in boiling point of solution in benzene in ∘^\circ C is x ×\times 10 −- 2. The value of x is ______________. (Nearest integer) [Atomic mass : C = 12.0, H = 1.0, O =16.0]

Step-by-Step Verified Solution

With benzene as solvent

Δ\Delta Tb = i Kb m

Δ\Delta Tb = 12{1 \over 2} ×\times 2.6 ×\times 1.22/Mw100/1000{{1.22/{M_w}} \over {100/1000}} .... (1)

With Acetone as solvent

Δ\Delta Tb = i Kb m

0.17 = 1 ×\times 1.7 ×\times 1.22/Mw100/1000{{1.22/{M_w}} \over {100/1000}} ..... (2)

(1) / (2)

ΔTb0.17=12×2.6+1.22/Mw100/10001×1.7×1.22/Mw100/1000{{\Delta {T_b}} \over {0.17}} = {{{1 \over 2} \times 2.6 + {{1.22/{M_w}} \over {100/1000}}} \over {1 \times 1.7 \times {{1.22/{M_w}} \over {100/1000}}}}

Δ\Delta Tb = 0.262{{0.26} \over 2}

Δ\Delta Tb = 13 ×\times 10 −- 2

⇒\Rightarrow x = 13

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