The general mass balance equation is: In - Out + Generation - Consumption = Accumulation If the balanced quantity is a non-reactive species (neither a product or reactant), which terms should be set to zero? In Out Generation Consumption Accumulation

Generation and consumption should be set to zero.

Explanation:

In the case where the species are non-reactive, the Generation and Consumption should be set to zero.

The Generation term becomes different from zero when there is a reaction that changes the mass balance and this change didn't come from the inflow of mass.

The Consumption term also refers to a reaction where reactants are being consumed in a chemical reaction, differentiating it from the exit flow.