## Entropy units

$\Delta G^{\circ}= \Delta H^{\circ} - T \Delta S^{\circ}$

$\Delta G^{\circ}= -RT\ln K$

$\Delta G^{\circ}= \sum \Delta G_{f}^{\circ}(products) - \sum \Delta G_{f}^{\circ}(reactants)$

Parker Smith
Posts: 102
Joined: Thu Jul 25, 2019 12:15 am

### Entropy units

So for a lot of the calculations I've been seeing in the book, the solutions book plugs in the entropy value in Joules and leaves the Enthalpy value in kilojoules. The units don't match, so I'm assuming you change them to match either in joules of kJ. Is this correct?

Naji Sarsam 1F
Posts: 104
Joined: Sat Aug 17, 2019 12:18 am

### Re: Entropy units

The units for entropy and enthalpy may be joules or kilojoules, it is just whatever is most useful for the number of joules there are. However, when doing calculations that include entropy and enthalpy in an equation, of course, you must match up their units--most of the time to joules.

gabbymaraziti
Posts: 111
Joined: Wed Sep 18, 2019 12:19 am

### Re: Entropy units

I'm sure either are fine, but if you have a large number of joules (1000+), it might be more useful to provide the answer in kilojoules.

Viviana Velasquez
Posts: 97
Joined: Sat Jul 20, 2019 12:15 am

### Re: Entropy units

I think either Joules or kilo joules is fine as long as you stay consistent throughout the entire problem to make sure no calculation mistakes are made. I would just make sure to read if the question asks for any units in specific

Erik Buetow 1F
Posts: 96
Joined: Fri Aug 30, 2019 12:15 am

### Re: Entropy units

Either one is fine, I think what you need to look out for is units during the calculations, especially regarding the constants that you are using. Also be sure to pay attention to what is being asked in the question as he might specify which one he wants the answer in.

Edmund Zhi 2B
Posts: 118
Joined: Sat Jul 20, 2019 12:16 am

### Re: Entropy units

Just make sure that in calculations, if you end up with L * atm, multiply it by a conversion to joules. It's 101.3 I believe

Eva Zhao 4I
Posts: 101
Joined: Sun Sep 29, 2019 12:16 am

### Re: Entropy units

As a general rule of thumb, try to write out the units as you're working through the problem since problems often give you a value in kJ, but the constants you use involve J. Otherwise unless the problem specifies, you can leave your answer in J or kJ. The answer key likely leaves the answer in kJ when the answer value is larger, as others have said.

305421980
Posts: 101
Joined: Sat Sep 07, 2019 12:16 am

### Re: Entropy units

Normally, because constants use J (like R) you just change all of them to match so the number comes out right.