Question

You only have a sample of a hydrocarbon of unkown formula. You only know that the molecule contains only C and H. You analyze the hydrocarbon by combusting a 1.230 g sample in excess oxygen to produce CO2 and H2O. You collect 3.726 g of CO2 produced by the reaction.

a) determine the moles of CO2 produced.

b) determine the moles and grams of C in CO2 produced. (Note that this is the same as moles and grams of C in your hydrocarbon sample)

Please explain, thank you!

Answer 1

Given that combustion of 1.230 g of unknown hydrocarbon produced 3.726 g CO2 .

a) Moles of CO2

Mass of CO2 = 3.726 g

Molar mass of CO2 = 44 g/mol

Moles of CO2 = mass / molar mass =3.726 g/ 44 g/mol = 0.085 mol

Therefore, moles of CO2 = 0.085 mol

b)  moles and grams of C in CO2

Mass of carbon present in 3.726 g of CO2 = 3.726 g x molar mass of carbon/ molar mass of CO2

= 3.726 g x 12 (g/mol) / 44 (g/mol)

= 1.016 g

Therefore, Mass of carbon = 1.016 g

Moles of carbon = mass / molar mass = 1.016 g / 12 g/mol = 0.085 mol

Therefore, moles of carbon = 0.085 mol