What does rate law depend on?

• A. Concentrations of reactants
• B. Temperature
• C. Pressure
• D. Solvent dielectric constant

Answer: (A)

The rate law tells you how the reaction rate changes as the concentrations of reactants change, under fixed temperature and other conditions. It has the form rate = k [A]^m [B]^n, so the variables in the expression are the reactant concentrations, with exponents giving the reaction orders. Temperature affects the rate by changing the rate constant k (often via the Arrhenius equation), not the way the rate depends on concentrations. Pressure can alter concentrations for gases and thus affect the observed rate, but the rate law itself is written in terms of concentrations. The solvent's dielectric constant can influence k as well, by stabilizing transition states, but it does not define how the rate depends on concentrations. So, the rate law directly depends on the concentrations of reactants.