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Heat Transfer Equations

Posted: Mon Jan 18, 2016 1:07 pm
by HoganFenster2E
When do we use Q=C x Delta T versus Q=n x C x Delta T? For example in question 8.53 we needed to find the heat released from burning 1.40 grams of CO in a bomb calorimeter and the equation q=C x Delta T was used. Why was this equation used and why do we sometimes include the moles/grams (n) in the equation?

Re: Heat Transfer Equations

Posted: Mon Jan 18, 2016 8:05 pm
by Bryce Bentley 1l
The equation Q=C x Delta T is used when we are given the total heat capacity for substance. this equation, Q=n (or mols)x C x Delta T, is used when we only know the specific (or molar) heat capacity of a substance and want to find the total amount of heat released or absorbed. Always pay attention to the units, if they are cancelled out then you should be on the right track for an equation. Also, when calorimeter's are used, the equations tend to give you the total heat capacity so you wont have to worry about moles or grams.

Re: Heat Transfer Equations

Posted: Tue Jan 19, 2016 12:46 pm
by Chem_Mod
The above discussion is correct. It depends on the heat capacity you are given. For specific heat capacity which is J/gK, you must have the amount of substance in gram (so that they cancel out g). For molar heat capacity, you will need the moles of the substance for the same reason. You want to end up with J.