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I'm still extremely confused on how gases could have multiple molar heat capacities. If you were to change the pressure or volume of a gas, you technically don't have to change the amount of moles of gas within the container right?
Cv denotes the heat capacity of a gas at a constant volume while Cp denotes the heat capacity of a gas at constant pressure. We have two values because, when heating takes place at constant pressure, some of the heat is used to do expansion work rather than raise the temperature of the system. For a more thorough explanation, read section 8.9 in the textbook.
For measuring heat transfer, the equation q=(n)(Cp)(delta T) relates molar heat capacity at a constant pressure with moles. If one were to change, the other would change accordingly. The relation changes if it is at constant volume instead.
I'm still confused on the reason why there are two separate molar heat capacities. I know that substances expand when heated which would change the heat capacity assuming we have constant pressure, but what happens if we have a constant volume? How would having a constant volume affect molar heat capacity for a gas?
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