Final answer:
The rate law for the elementary step Cl + CO → ClCO is given by rate = k[Cl][CO], where 'k' is the rate constant for this step.
Step-by-step explanation:
The rate law for the elementary step Cl + CO → ClCO is based on the stoichiometry of the reaction and the molecularity of the elementary step. Since the reaction involves the collision of chlorine and carbon monoxide molecules, the rate law for this step would be rate = k[Cl][CO], where 'k' is the rate constant for this step. This relationship is direct since it is for an elementary step, in contrast to an overall rate law which may require experimentally determining the rate-determining step.