一级反应动力学、二级反应动力学基本原理

Rate
=
concentration change time change
反应速率=△浓度/△时间
Rate = ___in__[p_r_od_u_c_ts_]___ = ____in__[r_e_ac_ta_n_t_s]__ change in time change in time
• Rate has units of moles per liter per unit time - M s-1, M h-1
2N2O5(g) 4NO2(g) + O2(g)
Rate of reaction
=
-
1 2
[N2O5] t
=
1 [NO2] 4 t
=
[O2] t
• Rate may be expressed in three main ways: •反应速率主要有以下三个表达方式： 1. Average reaction rate: a measure of the change in concentration with time
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
Rate of reaction
Biblioteka Baidu=-
1 a
[A] t
=-
1 b
[B] = t
1 c
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
“m”指关于物质A的反应级数，由实验确定。
“k” = rate coefficient (or specific reaction rate coeff.); determined for a specific reaction at a specific temp
“K”=速率常数（或特定的速率系数），由特定温度下的具体反应 确定
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
- 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
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
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)
AR=a=t=e>Lpraowduscts
-
dA
=
k
Reaction
× [ A]m
rate
dt
“m” indicates the order of the reaction with respect to species “A”. Determined experimentally.
[C] t
=
1 d
[D] t
• 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