Delta H Calculation Units

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Kenneth Trang
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Joined: Tue Nov 25, 2014 3:00 am

Delta H Calculation Units

Postby Kenneth Trang » Mon Jan 12, 2015 12:53 am

How do we know when calculating for Delta H if the resulting units will be either in "kJ" or "kJ/mol"? Or does it not make a difference?

Chem_Mod
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Re: Delta H Calculation Units

Postby Chem_Mod » Mon Jan 12, 2015 1:44 am

The values of enthalpy given in tables is in kJ/mol, since these values don't assume anything about the scale of your reaction. Similarly, if a problem simply asks for the enthalpy of a reaction without specifying mass or moles, then the answer will be in kJ/mol. But if for example the problem says that 2 moles of octane are burned, but in your balanced reaction the coefficient of octane is 1, then you should multiply the enthalpy in kJ/mol by 2 mol to get something in just kJ.

Ishkhan 3O
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Joined: Fri Sep 26, 2014 2:02 pm

Re: Delta H Calculation Units

Postby Ishkhan 3O » Tue Jan 13, 2015 9:04 pm

Well even if one did not know the units of delta H, you could cancel out of units when finding delta H and be left with the correct units in the answer.


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