How many molecules of ethanol (c2h5oh) (the alcohol in alcoholic beverages) are present in 160 ml of ethanol? the density of ethanol is 0.789 g/cm3. n =?
Density = mass / volume mass = density x volume mass = 0.789 x 160 = 126.24 grams
From the periodic table: mass of carbon = 12 grams mass of hydrogen = 1 grams mass of oxygen = 16 grams molar mass of ethanol = 2(12) + 5(1) + 16 +1 = 46 grams
number of moles = mass / molar mass number of moles = 126.24 / 46 = 2.744 moles
Each mole contains Avogadro's number of molecules. Therefore: number of molecules = 2.744 x 6.02 x 10^23 = 1.6518 x 10^24 molecules
