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Hydrocarbon combustion problem!

how do i solve this?
10cm3 of a gaseous hydrocarbon was mixed with excess oxygen and ignited. The gas volumes were measured at room temperature and pressure before and after combustion and it was found that the total gas volume had contracted by 20 cm3 . Given that combustion was complete, the formula of the hydrocarbon was
A C4 H4
B C4 H6
C C4 H8
D C4 H10
Reply 1
You Have to use ratios
volume of H20 = initial contraction = 20cm3
from the question we know number of C is 4

CO2 : H20
10 : 20
4 : x
x=8
since there are two H atoms, we have to divide X by 2 therefore X=4. Answer is A
i recommend you check this thread, they have done a much better job explaining it. hope it helps:smile:
http://www.thestudentroom.co.uk/showthread.php?t=2961109
(edited 8 years ago)

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