Verified Solution • 2025–26 Session moderate

QJEEM22Ch7fd6: JEE Main 2022 Chemistry - Class 12 JEEM22Ch7fd6 Solution: Solute A associates in water. When 0.7 g of solute A is…

Solute A associates in water. When 0.7 g of solute A is dissolved in 42.0 g of water, it depresses the freezing point by 0.2 ∘^\circ C. The percentage association of solute A in water, is :

[Given : Molar mass of A = 93 g mol −- 1. Molal depression constant of water is 1.86 K kg mol −- 1.]

Multiple Choice Options

  • A 50%
  • B 60%
  • C 70%
  • D 80%

Step-by-Step Verified Solution

Since, ΔTf=ikfm\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{ik}_{\mathrm{f} m}

amp;m=0.793×100042amp;0.2=i×1.86×0.7×100093×42amp;i=0.6amp;α=i−11n−1=0.6−112−1=0.8\begin{aligned}&m=\frac{0.7}{93} \times \frac{1000}{42} \\\\&0.2=i \times 1.86 \times \frac{0.7 \times 1000}{93 \times 42} \\\\&i=0.6 \\\\&\alpha=\frac{i-1}{\frac{1}{n}-1}=\frac{0.6-1}{\frac{1}{2}-1}=0.8\end{aligned}

Hence, the percentage association of solute AA is 80%80 \% .

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