How do scientists know that CO2 has a heat of formation of -393.5 kJ?

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Offline taregg

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can you show me with calculate
« Last Edit: 03/03/2012 11:12:47 by chris »


Offline damocles

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Re: how to know that CO2 = -393.5 kj heat formation
« Reply #1 on: 01/03/2012 12:47:41 »
This quantity is determined by experiment. You can burn a weighed amount of graphite in a bomb calorimeter, and make a precise measurement of the temperature rise. You have previously calibrated the calorimeter so that you know how much heat is needed to raise its temperature by 1 K. A number of precautions and corrections are needed to obtain a really precise and accurate value, but that is pretty much how it is done.

The usual way to 'know' facts like this is to look them up either in the NIST Webbook, or in the CRC Handbook of Chemistry and Physics.
1 4 6 4 1
4 4 9 4 4     
a perfect perfect square square
6 9 6 9 6
4 4 9 4 4
1 4 6 4 1


Offline imatfaal

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Re: how to know that CO2 = -393.5 kj heat formation
« Reply #2 on: 01/03/2012 17:02:16 »
this is homework (until shown otherwise).  Thanks to Damocles for his/her usual excellent answer - but thread locked nonetheless.

we learn through study by doing the work and research assigned to us by teachers/tutors, not by getting the answers from a forum.  If you have any homework problems then please feel free to ask the forum for guidance and help when you are stuck; and the knowledgeable members might well be able to provide that extra bit of information/technique that is necessary to complete the assignment - but it is counterproductive to get answers without putting in the time and effort to research the subject.
Thereís no sense in being precise when you donít even know what youíre talking about.  John Von Neumann

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