Which rate law expresses the rate as a function of reactant concentrations raised to powers?

• A. Integrated rate law
• B. Endothermic
• C. Differential rate law
• D. Catalyst

Answer: (C)

Think of the rate law as the equation that ties how fast a reaction proceeds to the actual concentrations of the reactants, with those concentrations potentially raised to powers that represent the reaction orders. The form that directly expresses the instantaneous rate in terms those concentrations raised to powers is the differential rate law: rate = k [A]^m [B]^n … Here m, n are the reaction orders determined experimentally, and the equation shows exactly how the rate changes as concentrations vary. An integrated rate law, in contrast, describes how concentrations change over time rather than how the rate depends on concentrations. Endothermic refers to whether heat is absorbed or released, not how the rate depends on concentrations. A catalyst speeds up the reaction but does not itself define the rate law form.