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AS level chemistry- help!!

Complete combustion of 50 cm3 of a hydrocarbon vapor gave 350 cm3
of carbon dioxide, both gas volumes being measured at the same temperature and pressure. The formula of the hydrocarbon could be

A C8H18
B C7H16
C C6H14
D C5H12


I don't understand. can someone help with this?
Original post by a.f.x.d
Complete combustion of 50 cm3 of a hydrocarbon vapor gave 350 cm3
of carbon dioxide, both gas volumes being measured at the same temperature and pressure. The formula of the hydrocarbon could be

A C8H18
B C7H16
C C6H14
D C5H12


I don't understand. can someone help with this?

So, we can start off by creating an equation for this combustion reaction:

Hydrocarbon + O2 ----> CO2 + H2O

So we combust 50cm3 of the hydrocarbon to produce 350cm3 of vapour. This vapour would be the CO2.
What we do then is simply 350/50 to get 7. Thus, 7 moles of CO2 are produced. This would mean that 7 moles of carbon are needed and if you look at the answer options, the answer is B.

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