A sample of ethanol, C2H6O, has a mass of 21.50 g. Calculate the number of ethanol molecules in the sample.

Question

Please Help I really indeed need help with this question!!! Like I got the number of moles of the ethanol being 0.46 but then I get confused from there.

Answer 1

To answer this question you must first go from grams to moles. Ethanol has a molecular mass of 46.07 grams / mole. You get this number by adding up the mass number on the periodic table of each element in the formula (eg: carbon is 12 x 2 = 24; H= 1 x6 = 6; O= 16 x 1; these masses are rounded but when you add them all up you get around 46).

21.5 grams * (1 mole /46.07 grams) = 0.46 moles. You multiply the number of moles by avogadro's number which is 6.02 X 10^23 molecules / mole = 2.7 X 10^23