At 400 K `1.5 g` of an unknown substance is dissolved in solvent and the solution is made to `1.5 L.` Its osmotic pressure is found to be `0.3` bar. Calculate the molar mass of the unknown substance.

Explanation

`Delta T_(b) = K_(b) m = K_(b) xx W_(2) xx 1000//M_(2) xx W_(1)`
`M _(2) = K_(b)xx W_(2) xx 1000//Delta T _(b) xx W_(1)`
`= 7.5 xx 0.75 xx 1000//0.15 xx 200 = 187.5 g mol ^(-1)`