The vapour pressure of water at 20 ℃ is 17.24 mm Hg. When 20 g of a non-ionic, substance is dissolved in 100…

The vapour pressure of water at 20℃ is 17.24 mm Hg. When 20 g of a non-ionic, substance is dissolved in 100 g of water, the vapour pressure is lowered by 0.30 mm Hg. What is the molecular mass of the substance?
  1. 200.8 g/mol
  2. 206.88 g/mol
  3. 210.5 g/mol
  4. 215.2 g/mol

Solution

p°-psp°=Xsolute
or
p°-psPs=nN
∴0.317.24=20M10018   {M=molar mass of solute}
∴M=20×18×17.240.3×100=206.88

Asked in: JEE-TOPICTESTS-CHEMISTRY

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