无机及分析化学新.pptVIP

一般写化学反应方程，只根据始态与终态写出反应结果，这种方程只表示反应前后的物料平衡关系，称为计量方程。例如： 基元反应简称元反应，如果一个化学反应，反应物分子在碰撞中相互作用直接转化为生成物分子，这种反应称为基元反应。 § 温度对反应速率的影响 速率方程中各反应物浓度项上的指数称为该反应物的级数； 所有浓度项指数的代数和称为该反应的总级数，通常用n 表示。n 的大小表明浓度对反应速率影响的大小。 反应级数可以是正数、负数、整数、分数或零，有的反应无法用简单的数字来表示级数。 反应级数是由实验测定的。 3. 反应级数 例如： 零级反应 一级反应 二级，对A和B各为一级 三级，对A为二级，对B为一级 负一级反应 1.5级反应 66 速率方程中的比例系数 k 称为反应的速率系数，以前称为速率常数，现改为速率系数更确切。 它的物理意义是当反应物的浓度均为单位浓度时k 等于反应速率，因此它的数值与反应物的浓度无关。在催化剂等其它条件确定时，k 的数值仅是温度的函数。 k 的单位随着反应级数的不同而不同。 4. 反应的速率系数 非基元反应速率方程的确定 范托夫等温方程 四、吉布斯自由能 a A + d D = g G + h H aA(aq)+bB(aq) gG(aq)+hH(aq) aA(g)+bB(g) gG(g)+hH(g) aA(aq)+bB(g) gG(g)+hH(aq) Chemical Equilibrium in gaseous state Describing Chemical Equilibrium Under proper conditions many chemical reactions can be made to go in either direction or other. At first both the concentrations of reactants and products change with time. CO(g)+H2O(g) CO2(g)+H2(g) Ag+(aq)+Cl-(aq) AgCl(s) O2(g)+2H2(g) 2H2O(g) However some times later, the change of the concentrations can be no longer detected over a long period of time. This observation is a clear indication that the reaction has stopped short of completion. In fact, the system has reached chemical equilibrium, the state where the concentrations of all reactants and product remain constant with time. Some reactions proceed rapidly; others are much slower. But in all cases a reacting system eventually reaches equilibrium. When the system reaches its equilibrium, it may appear that everything has stopped. However this is not the case. On the molecular level there is frenetic activity. Equilibrium is not static; it is a highly dynamic situation. That is to say both forward and reverse reactions occur at the same rate, or speed. Equilibrium Constant Science is based on experiments. From obser- vations of many chemical reactions,two Norw- egian chemists, Cato Maximilian Guldberg (1836 ~ 1902