一级反应动力学、二级反应动力学基本原理.ppt

Kinetics动力学 Thermodynamics determines whether and in which direction a reaction will happen, and what the concentrations of constituents are involved in the reaction 热力学决定了反应是否发生、反应的方向以及参与到反应之中的物质浓度问题。 Kinetics say how fast a reaction happens, sequence of steps in the reaction, and some of the factors that control the rates of reactions 动力学则说明反应发生的速率有多快、反应步骤的顺序以及控制反应速率的一些因素 Further Reading (Chapter 3 in Hobbs) Rate of reaction is typically measured as the change in concentration (moles/L) with time 反应速率通常通过浓度(mol/L)随时间的变化来测量 This change may be a decrease or an increase 改变可能是增加的也可能是减小的 Likewise the concentration change may be of reactants or products 同样，改变浓度的物质可能是反应物也可能是生成物 反应速率=△浓度/△时间 Rate has units of moles per liter per unit time - M s-1, M h-1 速率的单位是摩尔每升每单位时间，如M s-1、M h-1 Consider the hypothetical reaction 对于这个假设的反应 aA + bB  cC + dD We can write Note the use of the negative sign 注意负号的使用 - rate is defined as a positive quantity 反应速率被定义为正量 - rate of disappearance of a reactant is negative 那么，反应物的消耗速率就是负的 2N2O5(g)  4NO2(g) + O2(g) Rate may be expressed in three main ways: 反应速率主要有以下三个表达方式： Average reaction rate: a measure of the change in concentration with time 1、平均反应速率：浓度随时间变化的度量 2. Instantaneous rate: rate of change of concentration at any particular instant during the Reaction 2、瞬时速率：反应过程中某一特定瞬间的浓度变化速率 3. Initial rate: instantaneous rate at t = 0 - that is, when the reactants are first mixed 3、初始速率：t=0时即反应物最初混合时的瞬时速率， Rate Laws 速率定律 Rate law = a mathematical function describing the turnover rate of the compound of interest as a function of the concentrations of the various species participating in the reaction 速率定律：用来描述相关的化合物的转化速率的数学函数，即各种参与反应的物质的浓度的函数 May or may NOT have a theoretical basis可能有或没有理论基础 “Many reactions occur at a decreasing rate with increasing time because the reaction rate diminishes as the concentrations of the reactants diminish” “很多反应随着时间的增加反应速率逐渐减小？，因为反应物浓度减小会降低反应速率” Hobbs (2000) Rate Laws “m” indicates