Delta G Units

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Michele 2C
Posts: 23
Joined: Fri Sep 29, 2017 7:06 am

Delta G Units

Postby Michele 2C » Tue Feb 13, 2018 2:13 pm

So, I'm confused whether Gibbs free energy is reported in kJ or kJ/mole.
I know that molar Gibbs free energy implies kJ/mole. But standard Gibbs free energy is just reported in kJ (such as example 9.14, 9.15). But standard Gibbs free energy of formation is reported kJ/mole. Also, from 11.3, I know that the subscript 'r' also represents a molar quantity, so that would be reported in kJ/mole and the 'n' is just plugged in as a number (1 versus 1 mole). But how do we know in problems whether to use the molar quantity or not and whether to report Gibbs in kJ or kJ/mole? Is it okay to just always report it in kJ/mole?

Lily Guo 1D
Posts: 64
Joined: Fri Sep 29, 2017 7:03 am

Re: Delta G Units

Postby Lily Guo 1D » Tue Feb 13, 2018 2:29 pm

The rule that I usually follow is to use kJ for standard delta G of a whole reaction because the products aren't necessarily only present in 1 mole. Therefore, you can't say that standard delta G of a reaction is necessarily going to be kJ/mole; all that "standard delta G" implies is that the reaction occurs under standard conditions. If it's delta G of formation, however, then I think that kJ/mole is generally used.

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