Question

How many molecules of ethanol (c2h5oh) (the alcohol in alcoholic beverages) are present in 155 ml of ethanol? the density of ethanol is 0.789 g/cm3?

Answer 1

First convert volume to mass:

mass = 0.789 g/mL * 155 mL = 122.295 g

 

Then convert mass to number of moles:

number of moles = 122.295 g * (1 mole / 46 g) = 2.66 moles

 

Using avogadros number, we get the molecules:

number of molecules = 2.66 moles * 6.022 x 10^23 molecules / mole = 1.6 x 10^24 molecules