Complete combustion of 5.90 g of a hydrocarbon produced 17.9 g of co2 and 9.14 g of h2o. what is the empirical formula for the hydrocarbon?

Question

asked Oct 10, 2018 185k views

1 Answer

Derek Hewitt · Answer 1 · 2018-10-14T21:59:21+0000

A hydrocarbon is only composed of C atoms and H atoms. To get the empirical formula, get the moles of C and H.

The molar mass of CO2 is 44 g/mol and that of H2O is 18 g/mol.

moles CO2 = 17.9 g / (44 g / mol) = 0.407 mol

There is 1 mole of C per 1 mole of CO2, hence:

moles C = 0.407 mol

moles H2O = 9.14 g / (18 g / mol) = 0.508 mol

There is 2 moles of H per 1 mole of H2O, hence:

moles H = 0.508 mol * 2 = 1.02 mol

So so far we got:

moles C = 0.407 mol

moles H = 1.02 mol

Divide the two by the smallest number of moles, so divide by 0.407 mol:

C = 0.407 / 0.407 = 1

H = 1.02 / 0.407 = 2.5

Since there cannot be a decimal number of atoms, so multiply both by 2:

C = 1 * 2 = 2

H = 2.5 * 2 = 5

So the empirical formula is:

C2H5 (ANSWER)