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When to leave out reactants/products from enthalpy calculations

Posted: Fri Jan 31, 2020 7:08 pm
by Nick Fiorentino 1E
How do you know when a compound is in its purest form, aka when it won't impact enthalpy change?

Re: When to leave out reactants/products from enthalpy calculations

Posted: Fri Jan 31, 2020 7:45 pm
by VPatankar_2L
A compound is in its purest form when it is in its most stable form. An example of this is O2 which has an enthalpy of formation of zero because it is the most stable form of oxygen, whereas O3 would have an enthalpy of formation that was not equal to zero. Generally, gases are in their most stable form but a substance like carbon can be in its most stable form as solid graphite.

Re: When to leave out reactants/products from enthalpy calculations

Posted: Sun Feb 02, 2020 9:58 am
by Hui Qiao Wu 1I
To add on, the most stable forms won't affect enthalpy change only when calculating the enthalpy of formation.

Re: When to leave out reactants/products from enthalpy calculations

Posted: Sun Feb 02, 2020 10:16 am
by Caroline Zepecki
Can you assume that inert gasses wouldn't affect enthalpy calculations then?

Re: When to leave out reactants/products from enthalpy calculations

Posted: Sun Feb 02, 2020 10:57 am
by Jasmine 2C
I believe Dr Lavelle gave a list of gases that are in the purest form (O2, N2, etc). I think there should be a list in the textbook.