Calculating q (Enthalpy)

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Rhea Palsule
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Joined: Fri Sep 25, 2015 3:00 am

Calculating q (Enthalpy)

Postby Rhea Palsule » Wed Jan 20, 2016 12:13 am

In homework problem 8.53, the answer key uses the equation q= -C x T. Why is moles or grams not taken into account for this problem? Why is it necessary to use this equation rather than q= n x C x T?

Chem_Mod
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Re: Calculating q (Enthalpy)

Postby Chem_Mod » Wed Jan 20, 2016 12:53 am

It must have given the total heat capacity. Check to see if the units of the heat capacity given have moles or grams in the denominator. If they do not, then you don't need to multiply by moles or grams.

Rachel Lipman
Posts: 45
Joined: Fri Sep 25, 2015 3:00 am

Re: Calculating q (Enthalpy)

Postby Rachel Lipman » Sat Jan 23, 2016 10:55 am

If q is provided with units including mol-1/grams-1, then incorporating n into the final equation is incorrect. It is essential to look at the units for every calculated value in order to implement the right equations. I suggest ALWAYS writing out units for every number that way it is easy to notice which units cancel and which are carried through to the final answer. Keeping track of the units is essential especially in this case you are referring to because having not recorded the proper units, it is unknown which variation of an equation is used.


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