How to calculate the heat absorbed by a reversible process? Given a nonideal substance inside a box with diathermal walls, the pressure is increased reversibly. How do you calculate the heat absorbed?



I assume we use

dE = dq + dw = dq - pdV

=> dq = dE + pdV

But I'm not sure how to deal with the "dE" term.
I assume you mean the first law as 

$$dU = \delta q + \delta w$$

where $dU$ is the (state) change in internal energy, $\delta q$ is the (path dependent) work, and $\delta w$ is the (path dependent) work.

Saying the walls are diathermal says something about temperature (as you should confirm). Then, you should find a relationship between temperature change and internal energy change for the substance in your system.