Cv vs. Cp

[Kennedi2J]

I know that Cv= 3/2R and Cp=5/2R but how do know which one to use when calculating q=mCAT when it doesn't specify constant volume/pressure?

[Maia_Jackson_2C]

Usually you can tell from the context of the question whether or not there is a change in pressure or volume, but if not then I think you usually use Cv (that's what they said in the review session today but they didn't say why)

[Delaney Smith 1C]

Like what Maia said above, in the review session today they said that they have almost never used Cp and only Cv. But when you are calculating, you can also check to see if the compound is a monatomic or diatomic compound. If it's monatomic then use 3/2, but if it's diatomic use 5/2.