As the given moles OF ethanol = 0.040 now will find water moles that will b moles of water = 1 - 0.040=0.96 (substract 1 from etahnol mole fraction) now the mass of water = 0.96 mol x 18.02 g/mol=17.3 g where 18 is atomic mass of water mass of ethanol = 0.040 x 46 g/mol =1.84 g now mass of solution = 17.3 + 1.84=19.1 g that is mass of water +mass of etanol Now assume that the density of the solution = 1g/mL so the volume ofsolution = 19.1 mL = 0.0191 L so finally the molarity will be M = 0.040/ 0.0191=2.1 hope it helps
