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Topic: Thermochemistry problem.  (Read 4223 times)

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Offline necroramo

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Thermochemistry problem.
« on: October 19, 2008, 08:46:59 AM »
On complete comubsiton at costnat pressure, a 1.00-L sample of a gaseous mixture at 0 C and 1.00 atm *(STOP) evolves 75.65 kJ of heat If the gas is a mixture of ethane (C2H6) and propane (C3H8), what is the mole fraction of ethane in the mixture?


I really don't know where to start here.
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Offline sjb

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Re: Thermochemistry problem.
« Reply #1 on: October 19, 2008, 09:35:46 AM »
How much heat would one mole of ethane generate?

How much heat would one mole of propane generate?

How many moles of gas do you have in your sample?
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Offline necroramo

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Re: Thermochemistry problem.
« Reply #2 on: October 19, 2008, 11:22:44 AM »
Still nothing!

22.4 mol from STP at 1 liter.

84.7x + 103.8(22.4-x) = 73.65
84.7x + 2325.12 - 103.8x = 73.65
-19.1x + 2325.12 = 73.65
-19.1x = -2251.47
x = 118?!
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Offline necroramo

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Re: Thermochemistry problem.
« Reply #3 on: October 19, 2008, 12:13:21 PM »
IGNORE THAT I SCREWED UP THE DEFINITION OF STP

Even when I get it right, though, my equation still is not the right one.
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Offline enahs

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Re: Thermochemistry problem.
« Reply #4 on: October 19, 2008, 12:17:16 PM »
Answer SJb's first two questions first.
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Offline necroramo

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Re: Thermochemistry problem.
« Reply #5 on: October 19, 2008, 12:21:21 PM »
Enthalpies of formation:
C2H6 is -84.7
C3H8 is -103.8
?
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Offline sjb

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Re: Thermochemistry problem.
« Reply #6 on: October 19, 2008, 02:07:41 PM »
Quote from: necroramo on October 19, 2008, 12:21:21 PM
Enthalpies of formation:
C2H6 is -84.7
C3H8 is -103.8
?

What is the definition of complete combustion?
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