Question

How many molecules of ethanol (c2h5oh) (the alcohol in alcoholic beverages) are present in 140 ml of ethanol? the density of ethanol is 0.789 g/cm3?

Answer 1

An mL is also equivalent to cm³, signifying that 140 mL is equivalent to 140 cm³. The mass of ethanol is calculated by multiplying the density by the volume.

              mass = (140 cm³)(0.789 g/cm³)
                   mass = 110.46 g

Then, calculate the number of moles of ethanol by dividing the mass by the molar mass of ethanol equal to 46.07 g/mol.
               number of moles = (110.46 g/ 46.07 g/mol) = 2.4 mol

Then, multiply the number of moles by the Avogadro's number.
                    2.4 mol (6.022 x 10²³)
                 number of molecules = 1.445 x 10²⁴