Dichloroethane, a compound dat is often used 4 dry cleaning, contain carbon, hydrogen and chloride. It has mola mas of 99g/mol. Analysis of simple show dat is contain 24.3% carbon and 4.1% hydrogen

Question

Dichloroethane, a compound that is often used for dry cleaning, contain carbon, hydrogen and chloride. It has a molar mass of 99g/mol. Analysis of a simple show that is contain 24.3% carbon and 4.1% hydrogen. What is it's molecular formula?

Answer 1

Find the empirical formula:

Assume you have 100 g of material, then % equals grams.

24.3% C = 24.3 g C x 1 mol C / 12 g = 2.03 mols C

4.1% H = 4.1 g H x 1 mol H / 2 g = 2.05 mols H

This adds up to 28.4%. The rest must be chlorine (Cl) at 71.6%

71.6% Cl = 71.6 g Cl x 1 mol Cl / 35.5 g = 2.02 mols Cl

They all are about 2 moles so the empirical formula = CHCl (1 mol of each)

This empirical formula has a molar mass of 12 + 1 + 35.5 = 48.5 g/mol

The molar mass of the dilchloroethane is 99 g/mol

99 / 48.5 = 2.04

Therefore, molecular formula = C₂H₂Cl₂