standard enthalpy of formation  [ENDORSED]

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Ekayana Sethi 2K
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standard enthalpy of formation

Postby Ekayana Sethi 2K » Sat Jan 20, 2018 10:21 pm

I'm a little confused about the difference between enthalpy of formation and enthalpy of reaction? could someone explain please?

Yang Chen 2E
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Joined: Thu Jul 13, 2017 3:00 am

Re: standard enthalpy of formation

Postby Yang Chen 2E » Sat Jan 20, 2018 10:40 pm

This is what I wrote down:

when all reactants and products are in their standard states at 1 ATM of pressure, the reaction enthalpy is called the standard reaction enthalpy (ΔH°)

the standard reaction enthalpy for the formation of one molecule of a substance from its elements in their most stable form is called the standard enthalpy of formation (ΔHf°) (ALWAYS IN kJ/mol)

Gwyneth Huynh 1J
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Re: standard enthalpy of formation

Postby Gwyneth Huynh 1J » Sat Jan 20, 2018 10:51 pm

From what I understand, the reaction enthalpy measures the heat taken up or given off by any reaction with reactants and products. However, the enthalpy of formation measures the change in enthalpy between a substance and the elements that make up that substance in their standard state.

Simrina Desar Dis 1H
Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

Re: standard enthalpy of formation

Postby Simrina Desar Dis 1H » Sat Jan 20, 2018 11:05 pm

Also,
the standard enthalpy of formation of an element in its most stable form is zero.
This could be used to help distinguish between the two.

Scott Chin_1E
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Re: standard enthalpy of formation  [ENDORSED]

Postby Scott Chin_1E » Sat Jan 20, 2018 11:58 pm

Adding onto previous answers, I believe you will be using standard reaction enthalpies (from intermediate reactions) to calculate the enthalpy of formation (referring to the final reaction you wish to calculate for) in Hess's Law.


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