Constant Volume Heat of Combustion from heat capacity of calorimeter

[aruhland]

Homework Statement

A 0.009089 mol sample of an organic compound was burned in oxygen in a bomb calorimeter. The temperature of the calorimeter increased from 24.3 C to 31.1 C. If the heat capacity of the calorimeter is 4.38 kj/C, what is the constant volume heat of combustion of this compound, in kj/mol?

Relevant Equations

Qcal=heat capacity calorimeter * change in temperature
Q=nCdeltaT
Qcal=-Qrxn

Q=heat capacity calorimeter*(-)change in T*moles
=0.009089mol*-6.8C*4.38kj/C
=-0.2707kj/mol

This answer is wrong but it was the only one I could come up with right now. I just noticed units in the answer would be wrong too. Any suggestions?

 

[Borek]

Isn't heat of combustion given as a positive value?

 

[mjc123]

Q=nCdeltaT

What do the terms in this equation mean? What are their units? Have you done your calculation correctly?

 

[Borek]

Oh my, how I missed that :(