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 mahnitudes for the internal energy of gas in the two expansions.

Options

A. `DeltaH_(1) gt DeltaH_(2)`
B. `DeltaH_(1) lt DeltaH_(2)`
C. `DeltaH_(1) = DeltaH_(2)`
D. `DeltaH_(1) = DeltaU_(1)` and `DeltaH_(2) = DeltaU_(2)`

Explanation

We know that work done in a reversible expansion process is always greater than in a irreversible expansion process Using the first law of thermodynamics, `q = 0 = DeltaU +(-w)` Thus, decrease in `U` will be large in reversible adiabatic than irreversible adiabatic expansion and since `DeltaU = nC_(V)DeltaT`, we can conclude that `DeltaT` in reversible adiabatic expansion will be greater than in irreversible adiabatic expansion.
Now, `DeltaH_(1) = nC_(P)DeltaT_(1)`, and `DeltaH_(2) = nC_(P)DetaT_(2) rArr DeltaH_(1) gt DeltaH_(2)`