Mole fraction of ethyl alcohol in aqueous ethyl alcohol solution is 0. 25 hence the percentage of ethyl alcohol by weight is:

Given that the mole fraction of ethyl alcohol(C2H5OH) is 0.25

i.e. solution contains 0.25 mol EtOH and 0.75 mol H2O

Mol wt of EtOH is 46g/mol Therefore 0.25 mol = 0.25×46= 11.5 g of EtOH

Mol wt of H2O is 18 g/mol There fore 0.75 mol = 0.75×18=13.5 g of H2O

Total weight = 11.5+13.5=25 gms

Wt % of EtOH is (11.5/ 25) x 100 = 46 %