posted by Zedod .
What is molality of ethanol in water,if molar fraction of ethanol is 0.3?
XEtOH = 0.30
XH2O = 0.70
Take enough sample to be 1 mole. That means we will have 0.3 mol EtOH and 0.7 mole H2O. How many grams H2O is that? That will be 0.70 x 18 = 12.6 g or 0.0126 kg solvent.
Then m = moles EtOH/kg solvent.