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Help! AP Chem Help!

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skierdudeguy
Posts: 6574 - Karma: 81
ok. so.

basically: they burn a hydrocarbon and get 7.2 grams of water and 7.2 L of CO2 and STP.
i know the 22.4L/M thing, and i can obviously find moles of water (.399 mol H2O, .321 mol CO2).
but i need emperical formula! Help!
Jan 8 2008 12:34AM
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bkjumpr
Posts: 173 - Karma: 10
give up now, just guess.
Jan 8 2008 12:55AM
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skierdudeguy
Posts: 6574 - Karma: 81
thank you for your help, i knew i could turn to the arms of ns for help.
Jan 8 2008 1:02AM
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welcometojamrick
Posts: 498 - Karma: 21
StartFragment

Firstremember this is a combustion reaction so you'll have:

Hydrocarbon + O2 -----> H2O + CO2

so nextlook at what's given mass of H2O and the volume of CO2 soconvert the volume of CO2 to mass. Due to the law ofconstant conservation the mass for your reactants and products willbe the same. so you can now find the mass of you're hydrocarbon by usingthe formula (mass of products) - 32.02 (mass of O2) nowthat you have the mass you can use that to get you're empirical formula. also remember that empirical formula is just the proportions of the C toH, you can also figure since you're burning the hydrocarbon its more thenlikely an alkane which takes the form CnH2n+2.

I'm notexactly sure if this is the most streamlined way to approach theproblem or not hell i'm not sure if this will even give you the right answer its been too long since i've done problems like this. so hope it helps.

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Jan 8 2008 1:20AM
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skierdudeguy
Posts: 6574 - Karma: 81
you are beautiful and i love you.
Jan 8 2008 1:22AM
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