(a) What is a catalyst? (b) What is the difference between a homogeneous and a heterogeneous catalyst?

Key Concepts

Catalyst

A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It works by providing an alternative reaction pathway with a lower activation energy, allowing reactants to convert to products more efficiently. Catalysts are crucial in both industrial processes and biological systems, where they facilitate reactions that would otherwise occur too slowly.

Homogeneous Catalyst

A homogeneous catalyst is one that exists in the same phase (solid, liquid, or gas) as the reactants in a chemical reaction. This uniformity allows for better interaction between the catalyst and the reactants, often leading to more efficient reactions. An example is the use of sulfuric acid in the esterification of alcohols, where both the catalyst and reactants are in the liquid phase.

Heterogeneous Catalyst

A heterogeneous catalyst is one that is in a different phase than the reactants, typically solid catalysts interacting with gaseous or liquid reactants. This phase difference can lead to distinct reaction mechanisms, often involving adsorption of reactants onto the catalyst surface. An example is the use of platinum in catalytic converters, where the solid metal facilitates the conversion of gaseous pollutants into less harmful substances.