Question

Which of the following is always valid? Choose only ONE answer.

1. W = - P ∫ dV, for the calculation of work in a mechanically-reversible piston-cylinder arrangement

2. For any fluid undergoing a change in pressure, Cp = dH/dT.

3. ΔH = ΔU + Δ(PV)

4. ΔU = Q + W

5. ΔH = ΔU + P.ΔV

Answer 1

4. ΔU = Q + W

Step-by-step explanation:

Equation 4 corresponds to the definition of internal energy of a substance as part of a system. This equation is always valid and is fulfilled in all types of systems and refers to the known phrase:

"energy is neither created nor destroyed, transformed"........First Law of Thermodynamics