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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?
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.
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
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.
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.
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