What is the primary difference between homogeneous and heterogeneous catalysts?

The primary difference between homogeneous and heterogeneous catalysts lies in their phases relative to the reactants involved in the chemical reaction. Homogeneous catalysts are indeed in the same phase as the reactants, which usually means that both are either in a liquid or gas state. This allows for more effective interaction at the molecular level because the reactants and the catalyst can mix freely.

In contrast, heterogeneous catalysts exist in a different phase compared to the reactants. For example, a solid catalyst may be used to facilitate reactions in a liquid or gas phase. This difference in phase can influence how easily the reactants interact with the catalyst and can have implications on the efficiency of the reaction.

The other options either make claims that are not universally true or confuse the definitions of the catalyst types. For instance, it's not accurate to assert that one type of catalyst is always more effective than the other, as the effectiveness can depend on the specific reaction conditions. Thus, focusing on the phase relationship is crucial for understanding how these catalysts function.