Question

a solution was prepared by mixing ethanol (CH3CH2OH / d= 0.775 g/ml) with 350ml of water (H20 / d= 0.9940326). Assuming volumes were additive, determine the molarity of the solution knowing the mole fraction of water is 0.853.

help me resolve this please

Answer 1

Remember mass = volume x density and mols = grams/molar mass
XH2O = 0.853 = (mols H2O)/[(mols H2O + mols EtOH)]
0.853 = (g H2O/18)/[(g H2O/18) + (g EtOH/46)]
0.853 = (0.994*350/18)/[(0.994*350) + (0.775*V)/46]
The only unknown is V = volume of EtOH used. Solve for that.
Then 0.775 V/46 gives you mols EtOH, then mols EtOH/total volume in L give you molarity of EtOH. Post your work if you get stuck.