Standard Enthalpies

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TiffanyL1G
Posts: 61
Joined: Fri Sep 28, 2018 12:22 am

Standard Enthalpies

Postby TiffanyL1G » Mon Jan 28, 2019 5:44 pm

Do standard enthalpies only apply for gases? Is it like equilibrium, where any solid or liquid molecule in a chemical equation is ignored? Is it the same reason as equilibrium?

Lia Inadomi 1I
Posts: 62
Joined: Fri Sep 28, 2018 12:15 am

Re: Standard Enthalpies

Postby Lia Inadomi 1I » Mon Jan 28, 2019 6:54 pm

I beleive standard enthalpy is just when a pure element is under standard conditions of pressure and temperature, so it would just the phase of the element when it is under 1 atm and at 25 degrees C

Kayla Vo 1B
Posts: 60
Joined: Fri Sep 28, 2018 12:26 am

Re: Standard Enthalpies

Postby Kayla Vo 1B » Mon Jan 28, 2019 7:21 pm

The standard enthalpy of formation for an element in its standard state is zero. Standard state is like the physical state ( can be either solid, liquid, or gas) that a substance would be in under standard conditions (1.00 atm and 25 °C). Therefore, in standard conditions, the standard state for carbon is solid (graphite), for water is liquid, and for hydrogen is gas. Furthermore, as an example, the enthalpy of formation for Br2 in its standard state (liquid) is zero. However, the enthalpy of formation for Br (gas) is about 111.881 kJ/mol.


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