## Q in constant p and constant v

104422816
Posts: 17
Joined: Fri Sep 25, 2015 3:00 am

### Q in constant p and constant v

What are the two equations for q? The course reader has an equation for constant pressure. But what is it for variable pressure?

Erin 2I
Posts: 41
Joined: Fri Sep 25, 2015 3:00 am

### Re: Q in constant p and constant v

$q = (mass) \cdot C\cdot \Delta T$
C here is the specific heat capacity, which is constant.
There is also $q = (mole)\cdot C\cdot \Delta T$
The C here is the molar heat capacity, which is also constant. It should be noted that for all ideal gases, the molar heat capacity is $\frac{5}{2}R$ for CONSTANT PRESSURE, and $\frac{3}{2}R$
for CONSTANT VOLUME.
Also, at constant pressure, $q = \Delta H$, meaning that the heat calculated from any of the equations above is equal the the enthalpy of the reaction.

Chem_Mod
Posts: 19571
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 888 times

### Re: Q in constant p and constant v

The above discussion is correct! Just some clarification: Cp=5/2R and Cv=3/2R ONLY applies for MONOATOMIC ideal gases.