The rate of chemical reactions generally increases with temperature; this relation is described by which concept?

• A. Arrhenius principle (temperature dependence of reaction rate)
• B. Le Chatelier's principle
• C. Michaelis-Menten kinetics
• D. Hess's law

Answer: (A)

Temperature controls how fast reactions occur because higher heat gives molecules more energy and leads to more effective collisions. At higher temperatures, more molecules have enough energy to overcome the activation barrier, so the rate of product formation increases. This relationship is described by the Arrhenius principle, which is captured by the Arrhenius equation showing that the rate constant rises with temperature: k = A e^{-Ea/RT}. Here Ea is the activation energy—the minimum energy required for reaction—and the exponential term explains why even modest temperature increases can noticeably speed up a reaction.

Le Chatelier's principle, by contrast, is about how equilibria shift when a system is disturbed, such as by changing temperature or pressure—it's about where the reaction ends up, not how fast it goes. Michaelis-Menten kinetics focuses on how enzyme-catalyzed reaction rates depend on substrate concentration and enzyme characteristics, not general temperature dependence. Hess's law deals with enthalpy changes and energy accounting in reaction pathways, not kinetics. So the concept describing the temperature dependence of reaction rates is the Arrhenius principle.