In thermodynamics, which equation is utilized for calculating changes in state variables?

The equation used for calculating changes in state variables, particularly in the context of ideal gases, is the equation of state represented by PV = nRT. This equation connects pressure (P), volume (V), temperature (T), and the number of moles of gas (n) through the ideal gas constant (R).

This relationship allows you to derive various state variables under different conditions by rearranging the equation. For instance, if you know the initial state of a gas (P1, V1, T1) and some final state (P2, V2, T2), you can analyze how changes in one variable affect the others by using this equation.

In contrast, the other options listed do not adequately describe the calculation of changes in state variables in a straightforward manner. For example, the second option does not have a standard connection to state variables, and while the third option relates to kinetic energy and temperature, it is not focused on the state changes of gases. The fourth option, while hinting at a principle of thermodynamics concerning the relationship of pressure, volume, and temperature, is more specific to isothermal processes rather than general state variable changes. Thus, PV = nRT stands out as the most comprehensive and applicable equation for