Most Stable Form

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Tiffany Wu 1K
Posts: 19
Joined: Wed Sep 21, 2016 2:56 pm

Most Stable Form

Postby Tiffany Wu 1K » Fri Jan 13, 2017 12:14 am

For the standard enthalpy of formation of elements, do the ones in most stable form that equal 0 only include N2, O2, Cl2, Br2, and I2?

Christopher Liu 3J
Posts: 20
Joined: Fri Jul 15, 2016 3:00 am

Re: Most Stable Form

Postby Christopher Liu 3J » Fri Jan 13, 2017 12:29 am

There are more; for example, carbon's most stable form is graphite, or C(gr). Every element has a stable form, so I don't think we're expected to memorize all of them. I believe we'll be given a table of the ones we will use. If not, Lavelle will tell us which one's to memorize.

vsyacoubian2A
Posts: 63
Joined: Fri Jul 22, 2016 3:00 am

Re: Most Stable Form

Postby vsyacoubian2A » Fri Jan 13, 2017 7:04 am

All elements have their natural, most stable state. Look at the periodic table to see the state of matter each element is at room temperature. Metals will generally be solids, and Bromine and Mercury are liquids at room temperature.

In terms of having an enthalpy of formation value of 0, all single stand-alone elements, C, B, Be, etc. have enthalpy values of 0.
However, diatomic molecules (Br O N H F I Cl) also have enthalpy values of 0, because they are only bonding with the same element. No compounds are involved.

Michael Lesgart 1H
Posts: 26
Joined: Wed Sep 21, 2016 2:57 pm

Re: Most Stable Form

Postby Michael Lesgart 1H » Fri Jan 13, 2017 8:22 am

Would it be necessary to draw out the Lewis structure with a formal charge of 0 in order to determine a molecule's most stable form? Or is there another method that can be used?

Christine_Mavilian_3E
Posts: 30
Joined: Fri Jul 22, 2016 3:00 am

Re: Most Stable Form

Postby Christine_Mavilian_3E » Fri Jan 13, 2017 9:13 am

If I am correct, in this case, it's not necessary to draw out the Lewis structure with a formal charge of zero in order to determine a molecule's most stable form. In the course reader, it mentions that most reactions are given in their standard state. In most instances, it would be simple to determine that the stable state of elements such as N, O, F, Cl, Br, I, and H would be diatomic, and there are some such as C whose most stable form is graphite. There are instances that you will have compounds and in such cases you would look at their phases (i.e. gas, liquid, or solid) and you would use a chart to determine their corresponding standard enthalpies (i.e. there are several standard enthalpies for water: one would be for water vapor and the other for water in its stable state as a liquid).

I hope this helps!


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