In adiabatic expansion of a gas

In an adiabatic expansion of a gas

What is the source of the energy that does the work in an adiabatic expansion of a gas?

In an adiabatic expansion of a gas initial and final temperatures are T_(1) and T_(2) respectively, then the change in internal energy of the gas is

The magnitudes of enthalpy changes for irreversible adiabatic expansion of a gas from 1L to 2L is ∆H_(1) and for reversible adiabatic expansion for the same expansion is ∆H_(2) . Then

The magnitude of enthalpy changes for irreversible adiabatic expansion of a gas from 1 L to 2 l is Delta H_(1) and for reversible adiabatic expansion for the same expansion is Delta H_(2) . Then

The magnitude of enthalpy changes for irreversible adiabatic expansion of a gas from 1 L to 2 l is Delta H_(1) and for reversible adiabatic expansion for the same expansion is Delta H_(2) . Then

The magnitudes of enthalpy changes for irreversible adiabatic expansion of a gas from 1L to 2L is ∆H_(1) and for reversible adiabatic expansion for the same expansion is ∆H_(2) . Then

The magnitude of ethalphy changes for reversible adiabatic expansion of a gas from volume V_(1) to V_(2) (in L) is DeltaH_(1) and for irreversible adiabatic expansion for the same expansion is DeltaH_(2) . Then when DeltaU_(1) and DeltaU_(2) are the changes in magnitudes for the internal energy of gas in the two expansions.