A solution is prepared by dissolving 2.0 g of glucose and 4.0 g urea in 100 g of water at 298 K . Calculate the vapour pressure of the solution ,If the vapour pressure of pure water is ` 23.756` torr. (Molecular mass of urea = 60 and glucose = 180g `mol^(-1) ` )

Explanation

(i)`x_A =( n_A)/( n_A+n_B)`
` n_A = "No of moles water "`
`n_B = "No. of moles of glucose " `
`n_A =( 100)/( 18 ) = 5.555`
` n_B =(2)/( 180) = 0.0111`
Total moles ` (n_A+n_B) = 5.566`
(ii)Urea
` n_A = "No. of moles of water " `
` n_B=" No. of mole of urea " `
`n_A = 5.555`
` n_B=( 4)/( 60) = 0.0666 " moles of urea "`
Total moles ` = 0.555+ 0.066 moles `
`x_B = ( n_A)/( n_A+n_B) `
`= ( 5.555)/( 5.621) = 0.9882`
`P_B = P^(@) xx x_B `
`" "= 23.756xx 0.9882`
` P_B = 23.42 torr`