Calculating heat from H2 and O2

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Hydrogen and oxygen can combust to produce heat, and the heat generated can be calculated using the standard enthalpy of combustion, which is 287 kJ/mol for the reaction 2H2 + O2 → 2H2O. If the molar ratio of hydrogen to oxygen deviates from 2:1, complete combustion may not occur, affecting the total energy output. To calculate the energy produced, one can multiply the heat of combustion by the number of moles of hydrogen present. Additionally, while oxygen does not have a heat of combustion, if mixed with other combustible elements, their heats can be summed for total energy calculations. Temperature can be derived from heat energy, but requires knowledge of the initial temperature and specific heat capacity of the system.
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It is known that Hydrogen and Oxygen when combined can combust of course. So my question is : Can I calculate the heat produced from this combustion if I put a certain amount of hydrogen and oxygen?

Please Explain with an example.
 
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Butterfly_grl said:
It is known that Hydrogen and Oxygen when combined can combust of course. So my question is : Can I calculate the heat produced from this combustion if I put a certain amount of hydrogen and oxygen?

Please Explain with an example.

You certainly can calculate it. Since all H2/O2 molecules are identical, the same amount of energy will be released each time and so we can just quote a standard value from a textbook. I presume the reaction you have in mind is

2*H2 + O2 --> 2*H2O

which according to http://en.wikipedia.org/wiki/Hydrogen" has an enthalpy of combustion equal to 287 KJ/mol.

If you have a molar ratio different from 2:1 then complete combustion is impossible and the amount of energy you can extract will differ.
 
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Google "heat of combustion hydrogen", then multiply that number by the amount of hydrogen you have.
 
Alewhey said:
If you have a molar ratio different from 2:1 then complete combustion is impossible and the amount of energy you can extract will differ.

I think I understand this part but I've got a couple of questions.

1. When you say "complete combustion is impossible" that doesn't mean there's no combustion, there is but with a less or more amount. Right?

2. if such thing (molar ratio diffrent than 2:1) happened how can I calculate the energy then.

Again could you give me an example.

Thanks alot.
 
russ_watters said:
Google "heat of combustion hydrogen", then multiply that number by the amount of hydrogen you have.

If I have the amount of hydrogen ( number of moles ) then I can calculate the heat energy. Ok, but let me get this right.. We didn't mention the oxygen because it doesn't have heat of combustion, but if I mix the hydrogen with any element that has heat of combustion I'll just add them to get the final heat of combustion. SO Is that right?
 
Another Question :

How can you calculate the temperature when you have the heat energy? I think of course it needs another factor like the "initial temprature" but I don't know...

Thanks
 
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