Standard enthalpy of formation

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kennedyp
Posts: 56
Joined: Tue Nov 13, 2018 12:18 am

Standard enthalpy of formation

Postby kennedyp » Mon Jan 27, 2020 2:06 pm

Why exactly is the standard of formation of an element in its most stable form 0?

Megan Vu 1J
Posts: 101
Joined: Thu Jul 25, 2019 12:15 am

Re: Standard enthalpy of formation

Postby Megan Vu 1J » Mon Jan 27, 2020 2:15 pm

The standard enthalpy of formation for a stable element is zero because since it is diatomic, it requires no energy in order to form. Diatomic gases such as O2, I2, H2, and so forth are natural and form without needing energy, making it extremely stable.
To form an O2 for example, O2 -> O2, and there is no change in energy releasing.

haileyramsey-1c
Posts: 105
Joined: Thu Jul 25, 2019 12:18 am

Re: Standard enthalpy of formation

Postby haileyramsey-1c » Mon Jan 27, 2020 2:57 pm

The standard enthalpy of formation is zero because it is naturally occurring in its diatomic state. Since this state is preferred as it is more stable it requires no energy to form. Standard enthalpy of formation is the change in enthalpy when one mole of a substance is formed at 25 degrees celsius and 1atm. Since it is defined under these conditions, an element is the most stable. But, if conditions were to change another form of a substance may be more stable.

Ryan Lee 1E
Posts: 50
Joined: Sat Aug 17, 2019 12:16 am

Re: Standard enthalpy of formation

Postby Ryan Lee 1E » Mon Jan 27, 2020 9:28 pm

Yeah, as people have said, diatomic molecules are the in their most stable form, which means that under normal conditions, they already exist in this state. Therefore, it doesn't require additional energy to form them.

Katie Bart 1I
Posts: 104
Joined: Sat Aug 24, 2019 12:16 am

Re: Standard enthalpy of formation

Postby Katie Bart 1I » Tue Jan 28, 2020 11:47 am

Because elements exist in the form that requires the least amount of energy, so in their natural state, the standard enthalpy of formation would be zero.

005384106
Posts: 101
Joined: Sat Aug 24, 2019 12:16 am

Re: Standard enthalpy of formation

Postby 005384106 » Tue Jan 28, 2020 12:54 pm

As Lavelle talked about in lecture, Why is graphite the most stable form of carbon?

005384106
Posts: 101
Joined: Sat Aug 24, 2019 12:16 am

Re: Standard enthalpy of formation

Postby 005384106 » Tue Jan 28, 2020 12:56 pm

During Friday’s lecture, is method 3 a way to solve for enthalpy formation by subtracting the enthalpy of products by reactants?


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