What is the significance of a "basis" in reactor calculations for a chemical process?

• A. A basis defines the reactor's design pressure.
• B. A basis fixes a reference flow rate or amount (such as 1 hour, 1 mole, or 100 mol) to express conversions and rates.
• C. A basis determines the exact temperature of operation.
• D. A basis is a fixed reference temperature for calculations.

Answer: (D)

In reactor calculations, the basis is a fixed reference quantity used to express conversions and reaction rates in a consistent, scalable way. By choosing a basis such as 1 hour of operation, 1 mole of feed, or 100 moles, all quantities—conversions, yields, and rates—are written relative to that reference, which makes mass balances and rate expressions unambiguous and easy to scale to actual conditions. This normalization has nothing to do with setting design pressure or the operating temperature—the basis is about how you standardize amounts and flows. For example, if you adopt a mole basis, a conversion of 0.8 means 0.8 mole of reactant has reacted per mole of feed (depending on the exact definition used), and you can translate that to a per-hour or per-second rate once you know the basis. The temperature or pressure you operate at can then be applied to the basis-normalized quantities to obtain real-world numbers.