Standard Enthalpy

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Nga Mai 1F
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Joined: Fri Sep 25, 2015 3:00 am

Standard Enthalpy

Postby Nga Mai 1F » Sun Jan 10, 2016 11:07 pm

The course reader says that the standard enthalpy of formation of an element in its most stable form is 0. Is that why the enthalpy of O2 in the combustion of methane: CH4(g) + 2O2(g) --> CO2(g) = 2H2O(l) is 0? Why is this the case?

Annie Qing 2F
Posts: 28
Joined: Fri Sep 25, 2015 3:00 am

Re: Standard Enthalpy

Postby Annie Qing 2F » Sun Jan 10, 2016 11:09 pm

Yes. The standard enthalpy of formation for an element in its most stable form is 0 because we define the standard enthalpy of formation as the change in enthalpy between the product and the elements that make it up in its most standard form. Thus in the formation of O2, for example, O2 is both the product and reactant, so the change (and standard enthalpy of formation) is 0.


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