Standard entalpy of formation

Moderators: Chem_Mod, Chem_Admin

Tinisha 1G
Posts: 69
Joined: Fri Sep 28, 2018 12:17 am

Standard entalpy of formation

Postby Tinisha 1G » Mon Jan 28, 2019 12:36 pm

Which molecules have a standard enthalpy formation of 0? And why?

Laura Gong 3H
Posts: 89
Joined: Fri Sep 28, 2018 12:26 am
Been upvoted: 1 time

Re: Standard entalpy of formation

Postby Laura Gong 3H » Mon Jan 28, 2019 2:18 pm

By definition, the standard enthalpy of formation of an element in its most stable form is 0. This could include the diatomic molecules, H2, N2, O2, F2, Cl2, Br2, and I2 and transition metals in their solid form, and C in graphite form.

Anusha 1H
Posts: 65
Joined: Fri Sep 28, 2018 12:15 am

Re: Standard entalpy of formation

Postby Anusha 1H » Mon Jan 28, 2019 3:32 pm

Basically anything that is already in its standard form and doesnt have to change to form.
Elements are an example of this because theyre in their natural state

Jason Ye 2I
Posts: 33
Joined: Fri Sep 28, 2018 12:22 am

Re: Standard entalpy of formation

Postby Jason Ye 2I » Mon Jan 28, 2019 3:48 pm

Chemicals in their most stable form in which they cant be broken down anymore have a standard enthalpy of formation of 0

lindsey_ammann_4E
Posts: 61
Joined: Fri Sep 28, 2018 12:26 am

Re: Standard entalpy of formation

Postby lindsey_ammann_4E » Tue Jan 29, 2019 9:33 am

When a molecule is in its most stable state, the standard enthalpy of formation equals 0.

George Ghaly 2L
Posts: 66
Joined: Fri Sep 28, 2018 12:29 am
Been upvoted: 1 time

Re: Standard entalpy of formation

Postby George Ghaly 2L » Tue Jan 29, 2019 7:55 pm

When a molecule is at its basic state(elemental form including diatomic atoms) the standard enthalpy of formation is 0

Brian Kwak 1D
Posts: 88
Joined: Fri Sep 28, 2018 12:17 am

Re: Standard entalpy of formation

Postby Brian Kwak 1D » Wed Jan 30, 2019 4:15 pm

Molecules in their standard state (most stable) have an standard enthalpy formation of zero. It is important to note “Standard” which refers to a specific pressure which is 1 atm and a specific heat which is 25 degrees celcius. If a molecule is in its most stable state at 1 atm and 25 degrees celcius then it’s standard enthalpy formation is zero. Examples of such moles would be like O2(g) since oxygen is in its most stable state (a gas) its enthalpy formation is zero. Or H2(g) has a standard enthalpy formation of zero because its in it’s most stable state. I hope this helps a bit.

Note: Two elements are liquid in their standard state: mercury and bromine.

Eleven elements are gas in their standard state. All of the noble gases (He, Ne, Ar, Kr, Xe, Rn) as well the halogens flourine and chlorine. Hydrogen, oxygen and nitrogen are the others.

All other elements are solid in their standard state.


Return to “Phase Changes & Related Calculations”

Who is online

Users browsing this forum: No registered users and 3 guests