The relationship between molar masses of the two solvents is MX=43MY The relative lowering of vapour pressure of the two solutions is (PΔP)X=m(PΔP)Y But, the relative lowering of vapour pressure of solutions is directly proportional to the mole fraction of solute. Given 5 molal solution, means 5 moles of solute are dissolved in 1 kg ( or 1000 g ) of solvent. The number of moles of solvent =M1000 g The mole fraction of solute =1000/M5 =M×10005 hence MX×10005=m×MY×10005. Substitute equation (i) in equation (ii) 43×MY×10005=m×MY×10005 m=43
Two 5 molal solutions are prepared by dissolving a non-electrolyte, non-volatile solute separately in the solvents X and Y. The molecular weights of…
JEE Main 2018 — Chemistry Physical Chemistry
2018mcqhard
Two 5 molal solutions are prepared by dissolving a non-electrolyte, non-volatile solute separately in the solvents X and Y. The molecular weights of the solvents are MX and MY, respectively where MX=43MY. The relative lowering of vapour pressure of the solution in X is " m " times that of the solution in Y. Given that the number of moles of solute is very small in comparison to that of solvent, the value of "m" is:
Official previous-year question
Held on 15 Apr 2018 · Verified 6 Jul 2026.
Options
- A
43
- B
21
- C
41
- D
34
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