Chemistry Last minute help

Hey guys I'm so stuck on this w and as its multiple choice there's no explanation in ms!

10cm3 of a pure hydrocarbon was completly combusted in 70cm3 oxygen (excess).

The final gaseous mixture was 30cm3 Carbon dioxide and 20cm3 unreacted oxygen.

What is the formula of the hydrocarbon?
A) C2H4
B)C2H6
C) C3H6
D)C3H8

Thanks

Reply 1

Dynamic_Vicz

Volume is proportional to the amount of a substance.

You know that the oxygen is in excess so the limiting agent is the hydrocarbon.

Take 10 cm³ to be proportional to 1 mol.

You know that for a complete combustion : hydrocarbon + AOxygen - > Bcarbon dioxide + Cwarter where A, B and C are the relative moles of each substance in the reaction.

For an incomplete combustion: hydrocarbon + DOxygen - > Ecarbon monoxide + Fwater where D, E and F are the relative moles of each substance in the reaction.

Balance the constants to get the hydrocarbon.

(edited 6 years ago)

Reply 2

Emmaboyd

Thank you!