- #1

- 1,528

- 593

- Homework Statement
- Compute the entropy change of n moles of an ideal gas that is heated from [itex]T_i[/itex] to [itex]T_f[/itex] at constant volume. You know the heat capacity of this gas is [itex]C_p(t)[/itex].

- Relevant Equations
- For an ideal gas $$C_p - C_v = nR$$.

This is my first post of a homework problem, and I am just trying to make sure I am not missing anything as I help a child who is taking a college class on this stuff this summer. And to be clear, just trying to help her understand stuff, not help her with the homework problem. So I won't go through all the steps or give the explicit equation for [itex]C_p(t)[/itex] or anything.

To me this seems like it should be very straightforward. Since this is a constant volume process, [itex]\delta q = C_v(T) dT = (C_p(T)-nR) dT[/itex], from which we can get dS and integrate. Am I missing something? I am mainly asking because the TA indicated to my child that they should just use [itex]\delta q = C_p(T) dT[/itex] since entropy is a state function, which makes no sense to me nd was of course very confusing to my kid (who also may have misunderstood the TA - I of course wasn't there).

But I am not confident about classical thermo since I don't know much am mostly self-taught so I don't want to "correct" what my kid heard from the TA without checking with folks here who know this stuff better than I do. Any enlightenment would be much appreciated.

Thanks,

Jason

To me this seems like it should be very straightforward. Since this is a constant volume process, [itex]\delta q = C_v(T) dT = (C_p(T)-nR) dT[/itex], from which we can get dS and integrate. Am I missing something? I am mainly asking because the TA indicated to my child that they should just use [itex]\delta q = C_p(T) dT[/itex] since entropy is a state function, which makes no sense to me nd was of course very confusing to my kid (who also may have misunderstood the TA - I of course wasn't there).

But I am not confident about classical thermo since I don't know much am mostly self-taught so I don't want to "correct" what my kid heard from the TA without checking with folks here who know this stuff better than I do. Any enlightenment would be much appreciated.

Thanks,

Jason

Last edited: