Name: arrhenius equation in reaction speed
Uploaded: 2023-04-30T18:28:32.000Z
Duration: 2 min 28 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Chemistry

Matter And Its Interactions

HS-PS1-5

effect-of-temperature-change-on-reaction-rate

Effect of Temperature Change on Reaction Rate

反应的速率定律定义了反应速率与反应物浓度之间的关系，该关系以速率常数“k”来表示。
速率常数通过阿伦尼乌斯方程描述了温度与反应分子的碰撞、取向以及活化能相关的动力学参数之间的关系。‘A’ 是一个称为阿伦尼乌斯因子或频率因子的常数。‘e’ 是一个指数因子，整合了以焦耳每摩尔为单位的活化能、气体常数以及以开尔文为单位的温度。
参数对温度的依赖性可以用碰撞模型来解释，该模型指出，反应分子必须以正确的取向发生碰撞，并具备足够的能量，才能引发化学反应。
频率因子包含两个组成部分——碰撞频率和取向因子。碰撞频率是指单位时间内分子碰撞的次数，而取向因子则描述了具有有利取向的碰撞发生的概率。
然而，只有少数碰撞会导致化学反应发生。这是因为反应分子必须克服一个能量壁垒——即活化能，才能转化为产物。
只有那些具有足够动能的分子在碰撞时才会拥有足够的势能，使化学键发生弯曲、拉伸或断裂，从而转化为一种称为过渡态或活化络合物的高能中间体。这种短暂存在且不稳定的活化络合物会释放能量，形成稳定的产物，其总能量低于反应物的总能量。
阿伦尼乌斯方程中的指数因子代表导致产物生成的有效碰撞所占的比例。温度升高会影响频率因子和指数因子。
在较高温度下，分子运动更快、更剧烈，且具有更高的热能，从而导致更有利的碰撞。
对于大多数反应，温度升高会导致频率因子和指数因子增大，从而提高速率常数，进而表现为反应速率加快。

温度变化对反应速率的影响

阿伦尼乌斯方程，


 许多化学反应的活化能和速率常数 k 相关。


 <img alt="Figure1" src="/files/ftp_upload/11698/11698_Equation1.svg" style="text-align: center; height: 30px;">


 在此方程中，R 是理想气体常数，其值为 8.314 J/mol·K，T 是以开尔文为单位的温度，Ea 是以焦耳每摩尔为单位的活化能，e 是常数 2.7183，A 是常数，称为频率因子，它与碰撞频率和反应分子的方向有关。



 频率因子 A 反映了反应条件有利于反应物分子之间正确定向碰撞的程度。 有效定向碰撞的概率增加会导致 A 值更大和反应速率更快。



 指数项 e−Eₐ/RT 描述了活化能对反应速率的影响。 根据分子运动理论，物质的温度是其组成原子或分子的平均动能的量度——较低的活化能导致更多的能量充分的分子和更快的反应。



 指数项还描述了温度对反应速率的影响。 温度越高，代表拥有足够能量 (RT)来克服活化势垒 (Ea) 的分子比例相应越大。 这会产生更高的速率常数值和相应更快的反应速率。



 反应物碰撞过程中形成产物所需的最小能量称为活化能（Ea）。 所需的活化能和碰撞反应物分子提供的动能的差异是影响化学反应速率的主要因素。 如果活化能远大于分子的平均动能，则反应将缓慢发生，因为只有少数快速移动的分子才有足够的能量进行反应。 如果活化能远小于分子的平均动能，则大部分分子将具有足够的能量，反应将快速进行。



 反应图广泛用于化学动力学中，以说明感兴趣的反应的各种性质。 它显示了化学系统在发生反应时能量如何变化，将反应物转化为产物。



 本文改编自 <a href="https://openstax.org/books/chemistry-2e/pages/12-5-collision-theory">Openstax, Chemistry 2e, Section 12.5: Collision Theory.
</a>

阿伦尼乌斯方程，

将许多化学反应的活化能与速率常数 k 关联起来。
该方程中，R 为理想气体常数……

Education

教育

JoVE Core

Organic Chemistry

有机化学

Unit 1

第一单元

Thermodynamics and Chemical Kinetics

热力学与化学动力学

KEY TERMS AND CONCEPTS

关键术语与概念

arrhenius equation in reaction speed

The Arrhenius equation connects activation energy, temperature, and the rate constant, k, for many chemical reactions. It helps explain why some reactions move slowly while others happen faster.

In this equation, R is the ideal gas constant, with a value of 8.314 J/mol·K. T is the temperature in kelvin, Ea is the activation energy in joules per mole, e is the constant 2.7183, and A is the frequency factor.

The frequency factor, A, describes how often reacting molecules collide and how well they are oriented during those collisions. Better orientation increases the chance of effective collisions. That leads to larger A values and faster reaction rates.

The exponential term, e−Ea/RT, shows how activation energy affects the reaction rate. Kinetic molecular theory says that temperature measures the average kinetic energy of atoms or molecules. When activation energy is lower, more molecules have enough energy to react, and the reaction is faster.

The same exponential term also shows the effect of temperature. At higher temperature, a larger fraction of molecules has enough energy, RT, to get over the activation barrier, Ea. This increases the rate constant and speeds up the reaction.

Activation energy is the minimum energy needed to form products during a collision between reactants. If Ea is much larger than the average kinetic energy of the molecules, only a few fast-moving molecules can react, so the reaction is slow. If Ea is much smaller than the average kinetic energy, many molecules can react, so the reaction proceeds quickly.

Reaction diagrams are often used in chemical kinetics to show how a system’s energy changes as reactants turn into products. They help visualize the energy barrier and the path from reactants to products. This text is adapted from Openstax, Chemistry 2e, Section 12.5: Collision Theory.

Arrhenius Equation in Reaction Speed

chemical reactions

Stoichiometry, Rates, and Equilibrium

Stoichiometry, reaction rates, and equilibrium explain how chemical reactions are measured and predicted. A balanced chemical equation shows the chemical formulas of the reactants and products in a chemical change. It also gives the relative amounts of each substance involved. Reaction stoichiometry helps predict how much reactant is needed to make a desired amount of product. It can also show how much product forms from a given amount of reactant. The amounts shown by a balanced equation are...

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gibbs free energy and thermodynamic favorability

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chemical and solubility equilibria

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rate law and reaction order

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effect of temperature change on reaction rate

The Arrhenius equation connects activation energy, temperature, and the rate constant, k, for many chemical reactions. It helps explain why some reactions move slowly while others happen faster. In this equation, R is the ideal gas constant, with a value of 8.314 J/mol·K. T is the temperature in kelvin, Ea is the activation energy in joules per mole, e is the constant 2.7183, and A is the frequency factor. The frequency factor, A, describes how often reacting molecules collide and how well...

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energy diagrams, transition states, and intermediates

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key terms and concepts

Explore how the Arrhenius equation links temperature, activation energy, and collision orientation to reaction speed in high school chemistry.

Arrhenius Equation in Reaction Speed | JoVE K12

organic chemistry

JoVE Core 有机化学（Organic Chemistry）使用简明易懂的动画视频课程解释立体化学、反应和机制的基本概念。 此外，科学家在行动视频展示了相关概念在当今世界各地实验室进行的经典和原创研究实验中的应用。

Minnesota Academic Standards in Science

9-12

3.2.1 9C.3.1.1.2

Florida Department of Education

Physical Science

SC.912.P.12

SC.912.P.12.12

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HS-PS1-1

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HS-PS1-4

Arrhenius Equation in Reaction Speed

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