Find the empirical formula.

Question

The compound known as diethyl ether, commonly referred to as ether, contains carbon, hydrogen, and oxygen. A 1.376g sample of ether was combusted in an oxygen rich environment to produce 3.268g of CO₂(g) and 1.672g of H₂O(g). Insert subscripts to complete the empirical formula of ether.

Answer 1

The object is to find the moles of C, H and O. We can find moles C and H from the data give for CO2 and H2O, as follows:

3.268 g CO2 x 1 mol CO2 / 44 g x 1 mol C / mol CO2 = 0.0743 moles C

1.672 g H2O x 1 mol H2O / 18 g x 2 mol H / mol H2O = 0.186 moles H

To find moles of O, we need to first find grams of O. We do this by subtracting g C and g H from 1.376 g sample.

grams C = 0.0743 mol C x 12 g /mol = 0.8916 g C

grams H = 0.186 mol H x 1 g / mol = 0.186 g H

grams O = 1.376 g - 0.8916 g - 0.186 g = 0.1984 g O

moles O = 0.1984 g x 1 mol O / 16 g = 0.0186 moles O

Summary:

moles C = 0.0743 moles

moles H = 0.186 moles

moles O = 0.0186 moles

Dividing all by 0.0186 to try to get whole numbers...

C = 0.0743 / 0.0186 = 4 moles C

H = 0.186 / 0.0186 = 10 moles H

O = 0.0186 / 0.0186 = 1 mole O

Empirical formula = C₄H₁₀O