Berekening van grootheden uit de eerste hoofdwet II

Recall that the first law of thermodynamics describes the relationship between the change in internal energy, the heat flow, q, and the work done, w.

For an ideal gas, both internal energy, U, and enthalpy, H, depend only on temperature. So, any change in temperature results in changes in U and H.

Because U and H are state functions, their changes depend only on the initial and final states.

To calculate the change in U, we integrate the heat capacity at constant volume over the temperature range. Similarly, any change in H is obtained by integrating the heat capacity at constant pressure over the same range.

However, q and w are path functions. Their values depend on the specific path taken between the initial and final states.

For a reversible process, we calculate w as the negative integral of p dV. For an ideal gas, we replace p with nRT divided by V and evaluate the integral. Once w is known, the first law allows us to measure the heat transfer q.