Under what condition will the change in enthalpy equal the change in internal energy for a given chemical system?

The change in enthalpy of a system when a chemical reaction occurs is equal to to change in internal energy of the system added to the change in the product of Volume times pressure of the system.

Now, change in enthalpy equal the change in internal energy for a given chemical system when the product of volume time pressure is Zero. That neither the does any work nor any work in done on the system.