Final answer:
The false statement about enthalpy is that the enthalpy change is always positive, while in reality, enthalpy change can be either positive or negative.
Step-by-step explanation:
The statement regarding enthalpy that is false is: 4) Enthalpy change is always positive. Enthalpy change can be both positive and negative, depending on whether the process is endothermic or exothermic, respectively.
Statement 1) is true because enthalpy is a state function, meaning its value depends only on the current state of the system, not the path taken to reach that state. Statement 2) is also true as the enthalpy change at constant pressure is indeed equal to the heat transferred to or from the system. Statement 3) correctly expresses that the enthalpy change equals the internal energy change plus the work done on or by the system at constant pressure, where the work is specifically the pressure-volume work.
Enthalpy (H) can be described as H = U + PV, where U is internal energy, P is pressure, and V is volume. Since U, P, and V are all state functions, so is H.