The chemical being pumped primarily determines which of the following?

The chemical being pumped is crucial in determining the casing materials used in the pump system. Different chemicals have various corrosive properties, temperatures, and viscosities that can affect the integrity and functionality of the pump. Therefore, selecting appropriate casing materials ensures that the pump can withstand the chemical composition without degrading, leaking, or failing over time.

For example, highly corrosive chemicals may require casing materials made of specialized alloys or coatings to prevent corrosion, while less aggressive chemicals could be handled by standard materials. This decision is fundamental in designs to enhance durability, safety, and effectiveness of the pumping system.

The other options relate to characteristics that, while important, are more influenced by factors such as the specific application needs, system design requirements, and pump configuration rather than solely the chemical properties. Casing size and impeller size rely on flow rate and system design considerations rather than directly on the nature of the chemical. Impeller speed may depend on the desired flow and pressure characteristic rather than being determined strictly by the chemical itself.