A solution contains non volatile solute of molecular mass `M_(2)`. Which of the following can be used to claculate the molecular mass of solute in terms of osmotic pressure ?

Answer

109 . 67 u

Explanation

`W_(B) = 1.25 g `
`W_(A) = 20 g = 0 . 0 2 kg`
`K_(f) = 1.86 Km^(-1)`
`= 1.86 K kg mol^(-1)`
`Delta T_(f) = T_(f)^(@) - T_(f)`
`= (273 . 15 - 271 . 94) K`
= 1 .21 K
`Delta T_(f) =K_(f) xx (W_(B))/(M_(B)) xx (1)/( W_(A) (kg))`
`M_(B) = (K_(f) xx W_(B))/(Delta T_(f) xx W_(A) (kg))`
`= ((1 . 86 K kg mol^(-1)) xx (1 . 25 g))/( (1 . 21 K ) xx (0 . 02 kg))`
`= (186 xx 125)/( 121 xx 2) g mol^(-1)`
`= 96 . 07 g mol^(-1) = 96 . 07 u` `