What is rate law?

• A. An expression in which the reaction rate will depend only on the concentration of the reactants
• B. The energy profile of a reaction
• C. The rate constant of a reaction
• D. The equilibrium constant

Answer: (A)

Rate law tells you how fast a reaction proceeds by describing how the rate depends on the concentrations of the reactants. It’s an equation like rate = k [A]^m [B]^n, where the exponents show how the rate changes with each reactant, and k is the rate constant that includes temperature and the mechanism. The key idea is that the rate is expressed as a function of reactant concentrations, with temperature effects folded into k. The energy profile is about activation energy and energy changes, not how the rate depends on concentrations. The rate constant is part of the rate law but isn’t the whole relationship. The equilibrium constant describes balance at equilibrium, not the instantaneous rate. So the option describing the rate law as an expression where the rate depends on reactant concentrations is the best choice.