Question

An organic compound contains only three elements carbon, hydrogen and oxygen. Its elemental analysis gave C, 38.71% and H, 9.67%. The empirical formula of the compound would be
(a)CHO
(b) CHO
(c) CH,O
(d) CH,O​

Answer 1

Explanation:

Find out the mass of each element by assuming a certain overall mass.

100 g is a good mass to assume when % is given

∴ 0.38/100 = 38.71 g C

likewise H = 9.67 g

O = 100 - ( 38.71 + 9.67)

    = 51.62 g

Covert mass into moles by dividing it by molecular mass

C = 38.71/12 = 3.22 moles

H = 9.67/1 = 9.67 moles

O = 51.62/16 = 3.22 moles  

Ratio of moles of each element. Divide it by a small number of moles i.e  3.22

C = 1, H = 9. 67/3.22 = 3, O = 1

∴ Formula will be CH₃O.