Enthalpy (note, not energy) is an extensive property, and is proportional to the mass/size of the system, so mass is already accounted for. CO2's enthalpy can be represented in the same equation.
The energy balance equation is a fundamental thermodynamic equation. It is inherently coupled with mass balance equations. If we didn't get this right, we wouldn't have been able to design chemical reactors all these years.
Unfortunately because enthalpy is a more abstract concept, it isn't very appealing to folks who like simplifications like calories in = calories out. It is, however, the correct concept.
The energy balance equation is a fundamental thermodynamic equation. It is inherently coupled with mass balance equations. If we didn't get this right, we wouldn't have been able to design chemical reactors all these years.
Unfortunately because enthalpy is a more abstract concept, it isn't very appealing to folks who like simplifications like calories in = calories out. It is, however, the correct concept.