https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:kinetics/x2eef969c74e0d802:concentration-changes-over-time/v/half-life-of-a-first-order-reaction 2021-01-30T09:09:57Z Half-life of a first-order reaction The half-life of a reaction is the time required for a reactant to reach one-half its initial concentration or pressure. For a first-order reaction, the half-life is independent of concentration and constant over time. Jay video https://cdn.kastatic.org/googleusercontent/taGFKReyy9XV_ogNXyVpZRXKVv0S45ilMElDc9XHlo9937KrIZU5LXVE9rOF5BAzUjmIsSe_D2EZ0r1giQExInf0UA Half-life of a first-order reaction The half-life of a reaction is the time required for a reactant to reach one-half its initial concentration or pressure. For a first-order reaction, the half-life is independent of concentration and constant over time. https://cdn.kastatic.org/ka-youtube-converted/e4qci9b2d3U.mp4/e4qci9b2d3U.mp4 496 Calculating rate constant https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:kinetics/x2eef969c74e0d802:concentration-changes-over-time/v/kinetics-of-radioactive-decay 2022-10-05T02:43:18.611402953Z Kinetics of radioactive decay The nuclei of radioactive elements decay according to first-order kinetics. As a result, the half-life equation and integrated rate law for radioactive decay processes can be derived from the rate laws for first-order reactions. The resulting equations can be used to find the rate constant k for a decay process and determine the amount of radioactive isotope remaining after a certain time period. Jay video https://cdn.kastatic.org/ka_thumbnails_cache/4bc9ceff-05c1-4743-8487-1bbd425d0b87_1280_720_base.png Kinetics of radioactive decay The nuclei of radioactive elements decay according to first-order kinetics. As a result, the half-life equation and integrated rate law for radioactive decay processes can be derived from the rate laws for first-order reactions. The resulting equations can be used to find the rate constant k for a decay process and determine the amount of radioactive isotope remaining after a certain time period. https://cdn.kastatic.org/ka-youtube-converted/Xnu--929bo4.mp4/Xnu--929bo4.mp4 473 Calculating rate constant https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:kinetics/x2eef969c74e0d802:concentration-changes-over-time/v/first-order-reaction-example 2021-01-30T17:12:39Z Worked example: Using the first-order integrated rate law and half-life equations In this video, we'll use the first-order integrated rate law to calculate the concentration of a reactant after a given amount of time. We'll also calculate the amount of time it takes for the concentration to decrease to a certain value. Finally, we'll use the first-order half-life equation to calculate the half-life of the reaction. Jay video https://cdn.kastatic.org/googleusercontent/AENQQSoW7a8MGcdNdnyyfPQD7GE5FLETy0_xuuULbTLpL0X_rJ1m1eDvyxJayD2_vB7SWS74wDDQl7ovq2y5ey0 Worked example: Using the first-order integrated rate law and half-life equations In this video, we'll use the first-order integrated rate law to calculate the concentration of a reactant after a given amount of time. We'll also calculate the amount of time it takes for the concentration to decrease to a certain value. Finally, we'll use the first-order half-life equation to calculate the half-life of the reaction. https://cdn.kastatic.org/ka-youtube-converted/fCdT2z0JcU8.mp4/fCdT2z0JcU8.mp4 620 Calculating rate constant https://www.khanacademy.org/science/revision-term-1-tg-chemistry-class-12/x1c9114a2545341f7:week-2/x1c9114a2545341f7:electrochemistry-and-chemical-kinetics/e/initial-rate-method 2025-04-25T10:33:27.740574314Z Initial Rate method Let's solve some problems to understand how rate can be written as a function of initial concentrations of the reactants. We will solve problems to visualise how rate gets affected when the initial concentration of either one or all the reactants is changed during an experiment. Aanchal Arora exercise https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:kinetics/x2eef969c74e0d802:activation-energy-and-reaction-rate/v/arrhenius-equation 2021-01-30T09:09:57Z The Arrhenius equation The Arrhenius equation is k = Ae^(-Ea/RT), where A is the frequency or pre-exponential factor and e^(-Ea/RT) represents the fraction of collisions that have enough energy to overcome the activation barrier (i.e., have energy greater than or equal to the activation energy Ea) at temperature T. This equation can be used to understand how the rate of a chemical reaction depends on temperature. Jay video https://cdn.kastatic.org/googleusercontent/mnLj2_ES7mzDdwc2LckrZEXT_Nz6nBa7SNJmJCEc-zwTKvJZRc-GbFUXyyxI6iVFYUMdEEl2egovn2cQXJOyc11k The Arrhenius equation The Arrhenius equation is k = Ae^(-Ea/RT), where A is the frequency or pre-exponential factor and e^(-Ea/RT) represents the fraction of collisions that have enough energy to overcome the activation barrier (i.e., have energy greater than or equal to the activation energy Ea) at temperature T. This equation can be used to understand how the rate of a chemical reaction depends on temperature. https://cdn.kastatic.org/ka-youtube-converted/zjhepBLtqug.mp4/zjhepBLtqug.mp4 564 Calculating rate constant https://www.khanacademy.org/science/physical-chemistry-essentials-class-12/x1dda8a4b826d5e6c:chemical-kinetics/x1dda8a4b826d5e6c:temperature-dependence-of-reaction-rate/e/arrhenius-equation 2026-04-08T00:54:09.631945657Z Arrhenius equation (Arrhenius parameters) Let's solve some problems to interpret the terms used in the Arrhenius equation. Let's learn about the physical significance of the Arrhenius parameters and more! Aanchal Arora exercise