Home
Class 12
CHEMISTRY
Calculate the vapour pressure of an aque...

Calculate the vapour pressure of an aqueous solution which contains `5 mass per per cent` of `urea`. The vapour pressure of pure water is `23.5 mm Hg`. The molar mass of `urea` is `60`.

Text Solution

Verified by Experts

A 5% aqueous solutionof urea means that out of 100 g of solution , urea is 5 g and water is 95g.
Weight of solute (urea) `w_(B) = 5 g`
Weight of solvent (water) , `w_(B) = 95 g`
Molar mass of urea ` M_(B) = 60`
Molar mass of water `M_(A) = 18`
Vapour pressure of water , `p_(A)^(@) = 23.75 mm Hg`
Vapour pressure of solution `p_(A) = ?`
According to Roult.s law , .
`(p_(A)^(@) = p_(A))/(p_(A)^(@)) =(w_(B)M_(A))/(w_(A)M_(B))`
or `" " (23.75-p_(A))/(23.75) = ( 5 xx 18)/(96xx60) `
or ` " "23.75 - p_(A) = (5xx 18 xx 23.75)/(95 xx 60) = 0.375`
or `" "p_(A) = 23.75 - 0.375 = 23.375`
`therefore ` Vapour pressure of solution = 23.375 mm Hg.
Promotional Banner

Topper's Solved these Questions

  • SOLUTIONS

    MODERN PUBLICATION|Exercise PRACTICE PROBLEMS|100 Videos

  • SOLUTIONS

    MODERN PUBLICATION|Exercise ADVANCED LEVEL (PROBLEMS)|21 Videos

  • SOLID STATE

    MODERN PUBLICATION|Exercise UNIT PRACTICE TEST|13 Videos

  • SURFACE CHEMISTRY

    MODERN PUBLICATION|Exercise COMPETITION FILE (OBJECTIVE TYPE QUESTIONS) (MATCHING LIST TYPE QUESTIONS)|2 Videos

Similar Questions

Explore conceptually related problems

Calculate the vapour pressure lowering caused by addition of 50g of sucrose (molecular mass = 342) to 500g of water if the vapour pressure of pure water at 25^(@)C is 23.8 mm Hg .

30 g of urea (M=60g mol^(-1) ) is dissolved in 846g of water. Calculate the vapour pressure of water for this solution if vapour pressure of pure water at 298 K is 23.8 mm Hg. (b) Write two differences between ideal solutions and non-ideal solutions,

Calculate the molality and mole fraction of the solute in an aqueous solution containing 6g of urea per 500g of water (Mol. Mass of urea = 60)

Calculate the vapour pressure lowering caused by the addition of 68.4 g of sucrose (molecular mass = 342) to 500 g of water if the vapour pressure of pure water at 25^(@)C is 20.0 mm Hg .