Chemistry: Finding empirical formula

Question

Question: A hydrocarbon undergoes complete combustion, with oxygen present, to produce CO2 and water. On collecting the two products it was found that 2.20 g of CO2 and 0.90 g of vapourised water were formed.

Use the given information given to work out an empirical formula for the produced organic compound.

Option:

1. CH
2. C2H5
3. CH2
4. CH3

(Ans: CH2)

Answer 1

Convert g CO₂ to moles CO₂ and then moles C

Convert g H₂O to moles H₂O and then moles H

2.20 g CO₂ x 1 mol CO₂ / 44 g = 0.05 mols CO₂ x 1 mol C / mol CO₂ = 0.05 mols C

0.90 g H₂O x 1 mol H₂O / 18 g = 0.05 mols H₂O x 2 mol H / mol H₂O = 1.0 mol H

Multiply both by 2 in order to get whole numbers and we have...

1.0 mol C

2mol H

Empirical formula = CH₂