Is enthalpy only defined for constant pressure?

Is change in enthalpy defined only at constant pressure? No. The definition of ΔH is ΔH=ΔU+Δ(PV) Simple as that. I know Q-W=del(U) And Q at constant pressure equals del(H) (enthalpy change).

How do you calculate enthalpy when pressure is not constant?

You can always define H = U + PV and get dQ = dH + V dP. When P = const then ΔQ = ΔH, and so you can say the change in enthalpy is equal to the heat required for an isobaric process. This is useful.

Under what conditions is the enthalpy change of a process equal?

If the only work done is a change of volume at constant pressure, the enthalpy change is exactly equal to the heat transferred to the system.

Does enthalpy change with pressure for ideal gas?

For ideal gas, V equals to RT over P from the equation of state. Then, (dH over dP) at constant T becomes zero. Thus, enthalpy does not depend on pressure at constant T and it is a function of temperature only.

What is the relationship between pressure and enthalpy?

Definition. The enthalpy H of a thermodynamic system is defined as the sum of its internal energy and the product of its pressure and volume: H = U + pV, where U is the internal energy, p is pressure, and V is the volume of the system.

What is the difference between change in enthalpy and change in internal energy at constant volume?

Enthalpy is a state function whose change indicates the amount of heat transferred from a system to its surroundings or vice versa, at constant pressure. The change in the internal energy of a system is the sum of the heat transferred and the work done.

Is the enthalpy change of a process equal?

According to the law of energy conservation, the change in internal energy is equal to the heat transferred to, less the work done by, the system. If the only work done is a change of volume at constant pressure, the enthalpy change is exactly equal to the heat transferred to the system.

What is the difference between change in enthalpy and change in internal energy?

The main difference between enthalpy and internal energy is that enthalpy is the heat absorbed or evolved during chemical reactions that occur in a system whereas internal energy is the sum of potential and kinetic energy in a system.