A combustion reaction involves the reaction of a substance with oxygen gas. The

Question

A combustion reaction involves the reaction of a substance with oxygen gas. The complete combustion of any hydrocarbon (binary compound of carbon and hydrogen) produces carbon dioxide and water as the only products. Hexane is a hydrocarbon that is found in gasoline. Complete combustion of hexane produces 6 L of carbon dioxide for every 7 L of water vapor (both measured at the same temperature and pressure). What is the ratio of carbon atoms to hydrogen atoms in a molecule of hexane?

(Simplify your answer completely.)

Explanation / Answer

the idea is this... for the reaction
.. a X + b Y ---> c XY
where X, Y, and XY are all gases at the same temperature and pressure, those coefficients, a, b, and c are VOLUME RATIOS... more on that when you cover gases in chapter 5 of your textbook :).

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meaning..
.. n CxHy + m O2 ---> 6 CO2 + 7 H2O... <=== the 6 and 7 are the volumes!

and because the O2 on the left contains neither C nor H..
therefore.. All of that C and H came from the isooctane.

meaning.. the ratio of C to H must be (6x1=6) C to (7x2=14) H

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you might think.. well what happens if n ? 1... say it's 2... or 8..
does that change the RATIO of C to H in the CxHy?

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