Chemical Kinetics Practice Test

For a first-order process, the half-life is t1/2 = ln 2 / k, so it depends on the rate constant k but not on the initial amount. Temperature affects k through the Arrhenius relationship: higher temperature raises k. Therefore, as temperature increases, the half-life decreases. An example like a thermal decomposition that follows first order fits this perfectly: heating the sample speeds up the reaction (larger k), so you reach half of the reactant remaining sooner (a smaller t1/2). The other descriptions don’t align with this behavior. A second-order process has t1/2 that depends on the initial concentration and, although k increases with temperature, the stated trend of t1/2 increasing with temperature isn’t generally correct. A zero-order process would have t1/2 that changes with k and initial concentration, not a constant value, so saying it’s constant with temperature is inaccurate. And a first-order process cannot have t1/2 increasing with temperature because t1/2 is inversely related to k, which grows with temperature.