JEE MAIN - Chemistry (2025 - 29th January Morning Shift - No. 1)
1.24 g of AX2 (molar mass 124 g mol−1) is dissolved in 1 kg of water to form a solution with boiling point of 100.015°C, while 25.4 g of AY2 (molar mass 250 g mol−1) in 2 kg of water constitutes a solution with a boiling point of 100.0260°C.
Kb(H2O) = 0.52 kg mol−1
Which of the following is correct?
Explanation
For $\mathrm{AX}_2:-\Delta \mathrm{T}_{\mathrm{b}}=\mathrm{K}_{\mathrm{b}} \times \mathrm{m} \times \mathrm{i}$
$$0.0156=0.52 \times \frac{0.01}{1} \times \mathrm{i}_{\mathrm{AX}_2}$$
$\Rightarrow \mathrm{i}_{\mathrm{AX}_2}=3 \Rightarrow$ complete ionisation
For $\mathrm{AY}_2:-\Delta \mathrm{T}_{\mathrm{b}}=\mathrm{K}_{\mathrm{b}} \times \mathrm{m} \times \mathrm{i}$
$0.026=0.52 \times 0.0508 \times \mathrm{i}_{\mathrm{AY}_2}$
$\Rightarrow \mathrm{i}_{\mathrm{AY}_2} \simeq 1 \therefore$ complete unionisation
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