Hydrocarbon empirical formula question

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SUMMARY

The empirical formula of the hydrocarbon burned in the problem is determined to be C3H8, which is propane. The total pressure of the gas mixture is 1.200 atm, with a partial pressure of H2O at 0.686 atm. Using the relationship between partial pressures and the number of molecules, the ratio of hydrogen to carbon can be established, leading to the conclusion that the hydrocarbon consists of three carbon atoms and eight hydrogen atoms.

PREREQUISITES
  • Understanding of gas laws, specifically the ideal gas law (pV=nRT).
  • Knowledge of Dalton's Law of Partial Pressures.
  • Familiarity with empirical formulas and molecular ratios.
  • Basic algebra skills for solving equations.
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  • Study Dalton's Law of Partial Pressures in detail.
  • Learn how to derive empirical formulas from combustion reactions.
  • Explore the ideal gas law applications in chemical reactions.
  • Practice problems involving hydrocarbon combustion and stoichiometry.
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Homework Statement


Q. A Hydrocarbon (CnHm) is burned completely in oxygen to produce a mixture of CO2 and H2O. The total pressure of mixture is 1.200 atm and partial pressure of H2O is 0.686 atm. What is empirical formula of Hydrocarbon



Homework Equations



pV=nRT
pa/ptotal = na/ntotal

The Attempt at a Solution


The answer is C3H8 aka Propane

Im so confused! I don't even know where to start with this!
 
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Find the partial pressure for the CO2. The partial pressures of the gases are proportional to the number of molecules, so you've immediately got the ratio of the number of H2O molecules to the number of CO2 molecules. This is almost m/n, but note that because of the H2 there are twice as many H's as H2O's, so you've really got the ratio of m/2 to n. It should then be easy to get the ratio m to n. Then you start guessing - if n=1 does m work out to an even number? If not, try n = 2 and so on.
 

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