Reaction Enthalpy and Reaction Internal Energy

[Kaitlin_Reeves_1C]

I'm still kind of confused on what the textbook means when it says, "The reaction enthalpy is less negative than the reaction internal energy for reactions that generate gases." Why would it always be less negative?

[Chem_Mod]

Because the system must use some of the energy to expand volume for the reaction products (gases).