Units of S and H

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MCracchiolo 1C
Posts: 55
Joined: Sat Jul 22, 2017 3:00 am

Units of S and H

Postby MCracchiolo 1C » Sun Feb 11, 2018 9:50 pm

When calculating problems that involve DeltaS and DeltaH, if you multiply the standard enthalpies of formation or standard molar entropies by the number of moles in the balanced chemical equation, why are your answers still in kJ/mol and J/(K*mol)?

Nickolas Manipud 1C
Posts: 60
Joined: Fri Sep 29, 2017 7:07 am

Re: Units of S and H

Postby Nickolas Manipud 1C » Sun Feb 11, 2018 9:57 pm

Because you just found the standard enthaply or molar entropy of 1 mole of some substance from the chemical reaction

Michelle Dong 1F
Posts: 110
Joined: Fri Sep 29, 2017 7:04 am

Re: Units of S and H

Postby Michelle Dong 1F » Tue Feb 13, 2018 7:12 pm

I'm pretty sure Dr. Lavelle said that he would accept either unit. However, for enthalpy of formation or standard molar entropy or Gibbs free energy of formation, it must be per mole because that's the definition of "formation".

Yixin Angela Wang 2H
Posts: 51
Joined: Thu Jul 27, 2017 3:00 am

Re: Units of S and H

Postby Yixin Angela Wang 2H » Thu Feb 15, 2018 2:58 am

I think the per mole part can be omitted, at least that's what I recall Dr. Lavelle saying. At least for this class.

Rishi Khettry 1L
Posts: 29
Joined: Fri Sep 29, 2017 7:05 am

Re: Units of S and H

Postby Rishi Khettry 1L » Fri Feb 16, 2018 11:05 am

Hi Megan!
Although sometimes understanding the units can be quite difficult, in class, Dr. Lavelle mentioned either unit would be correct.
Just be sure to make the units for your Gibbs Free Energy of formation to be in "per mole".
Good luck!


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