Standard Enthalpy of Formation from Most Stable Form

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Lily Guo 1D
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Joined: Fri Sep 29, 2017 7:03 am

Standard Enthalpy of Formation from Most Stable Form

Postby Lily Guo 1D » Sat Jan 13, 2018 4:13 pm

I know that the standard enthalpy of formation of an element in its most stable form is zero, but does that mean that the element begins in an unstable form and goes to its stable form, ex: N2 (l) ==> N2 (g)? Or would the element begin in its most stable form and then stay in its most stable form, ex: O2 (g) ==> O2 (g)?

Lindsay H 2B
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Re: Standard Enthalpy of Formation from Most Stable Form

Postby Lindsay H 2B » Sat Jan 13, 2018 4:30 pm

I think it implies that the element would begin in its most stable form

Gurshaan Nagra 2F
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Re: Standard Enthalpy of Formation from Most Stable Form

Postby Gurshaan Nagra 2F » Sat Jan 13, 2018 6:14 pm

When it is 0 it means the element began in its most stable from like the O2 example you described, the N2 example would not be 0

Jacob Cho 2L
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Joined: Fri Sep 29, 2017 7:05 am

Re: Standard Enthalpy of Formation from Most Stable Form

Postby Jacob Cho 2L » Sun Jan 14, 2018 12:14 am

The standard enthalpy of formation for an element in its most stable form is zero because, being already in its most stable form, it requires zero enthalpy of formation to get to its most stable form. There is no need for a change in heat to reach a form that it already exists in. Usually, we use this principle in our work because the elements are almost always found/used in their most stable form. When they are explicitly not in their most stable form, we would need to consider their enthalpies of formation which would then be non-zero values.


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