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If the boiling points of two solvents X and Y (having same molecular weights) are in the ratio 2: 1 and their enthalpy of vaporizations are in the ratio 1: 2, then the boiling point elevation constant of X is m times the boiling point elevation constant of Y. The value of m is (nearest integer).
ChemistrySolutionsJEE MainJEE Main 2023 (08 Apr Shift 2)
Solution:
2716 Upvotes Verified Answer
The correct answer is: 8

The boiling point elevation constant Kb of a volatile liquid is given by the following expression
Kb=RTb2MΔHv

Where Tb=boiling point of the liquid
            M=molar mass of the liquid
            ΔHv= Enthalpy of vaporisation

The boiling points of the two solvents are in the ratio 2:1, which means that the boiling point elevation constants are also in the ratio 2:1. Let's call the boiling point elevation constant of solvent X as (Tb)x, and the boiling point elevation constant of solvent Y as (Tb)y.
Given: Mx=My
Tbx=2Tby
2ΔHvx=ΔHvy
 KbxKby=212×21=81=m
 m=8

Therefore, the value of m is 8(nearest integer).

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