What is the molecularity of each of the following elementary reactions? Write the rate law for each. (a) Cl₂(g) → 2 Cl(g)

Key Concepts

Molecularity

Molecularity refers to the number of reactant molecules involved in an elementary reaction. It can be classified as unimolecular (one molecule), bimolecular (two molecules), or termolecular (three molecules). In the given reaction, Cl₂(g) → 2 Cl(g), the molecularity is unimolecular since only one molecule of Cl₂ is involved in the reaction.

Elementary Reaction

An elementary reaction is a single step process that describes the direct transformation of reactants into products. Unlike complex reactions, which may involve multiple steps, elementary reactions have a straightforward relationship between reactants and products. The reaction Cl₂(g) → 2 Cl(g) is an elementary reaction because it occurs in one step without intermediates.

Rate Law

The rate law expresses the relationship between the rate of a chemical reaction and the concentration of its reactants. For elementary reactions, the rate law can be directly derived from the stoichiometry of the reaction. In this case, the rate law for the reaction Cl₂(g) → 2 Cl(g) is rate = k[Cl₂], where k is the rate constant, indicating that the reaction rate depends on the concentration of Cl₂.