《工科基础化学第二版课件教学课件 ppt 作者 唐和清 主编第6章 电化学基础》由会员分享，可在线阅读，更多相关《工科基础化学第二版课件教学课件 ppt 作者 唐和清 主编第6章 电化学基础（122页珍藏版）》请在金锄头文库上搜索。
1、Energy,How to get electricity,electrical energy,Electrochemistry,化学工业出版社,chemicals,electrical energy,chemicals,氯碱工业,How to produce chemicals by electrolysis,Electrochemistry,第六章 电化学基础与金属腐蚀 Chapter 6 Electrochemistry and Corrosion of Metals,6.1 氧化还原反应与氧化还原平衡 6.1.1 氧化还原反应 Fe3+ + Cu+ = Fe2+ + Cu2+ Zn +
2、 Cu2+ = Zn2+ + Cu 是否是氧化还原反应？有无差别？,化学工业出版社,一般的氧化还原反应： 氧化剂与还原剂直接接触，实现电子的转移 电化学反应（electrochemical reaction） ： 反应物之间不直接接触，而是通过导体实现电子 的转移，还原剂失去的电子流经导体转移到氧化 剂，发生了电子的定向流动 电化学： 化学与电学的交叉学科，研究的是氧化还原反应 的化学能与电能的相互转化 电化学工业：以电化学反应操作为核心的工业,6.1.2 氧化还原平衡 无论是一般的氧化还原反应，还是电化学反应，都能在一定的反应条件下实现平衡，其平衡状态以及平衡移动满足普通的化学反应体系的平衡
3、与移动的基本规律,6.2 原电池与电极电势 Primary Cells and Electrode Potential,Spontaneous reaction,Zn(s) + Cu2+(aq) = Zn2+(aq) + Cu(s) DGo(298.15K) = -212.55 kJ mol-1,DGo(298.15K) 0,6.2.1 原电池 1原电池的组成,Are there any devices that directly convert the Gibbs function change into electrical energy ?,Yes. They are Primary c
4、ells. They are apparatuses directly converting electron transfer in a redox reaction into electrical energy.,Diannill cell (Discharging state),At Zn plate electrode： Zn - 2 e Zn2+ At Cu plate electrode： Cu2+ + 2 e Cu,Driving force：electromotive potential,图6-1 铜锌原电池的示意图,原电池 结构 Cell structure： negativ
5、e electrode, active materials for negative electrode (NAM), electrolyte, active materials for positive electrode (PAM), positive electrode 原电池 结构的图示 Graphic representation： negative electrode |NAM|electrolyte|PAM| positive electrode Diannill cell ： Zn|ZnSO4 (aq) | CuSO4 (aq) |Cu -) ZnZn2+(c1)|Cu2+(c
6、2)Cu (+ Where “|” stands for an interface and “| ” means a diagram c1和c2分别表示相应溶液的体积摩尔浓度，如果是气体，则改用分压（p）来表示,2.原电池热力学,对于电池反应，在恒温恒压可逆条件下放电时，系统对环境做的非体积功w是可逆电功(最大电功)。 可逆电功等于电池的电动势E与电量的乘积 w maxQ E - zFE rGm- zFE 如果原电池在标准状态下工作，则有：rGm- zFE,如果一个化学反应在恒温恒压可逆条件下进行，摩尔吉布斯函数变rGm与反应过程中系统能够对环境做的非体积功w之间存在如下关系： rGm w m
7、ax,Electromotive force of primary cell and Gibbs function change of cell reaction,A spontaneous redox reaction system can be used to construct a primary cell. Under conditions of constant temperature and constant pressure, all the chemical energy can be converted into electrical energy without any e
8、nergy loss, and the Gibbs function change of the cell reaction equals to the maximum work the cell can do. DrGm = DG = wmax = -QE = -nFE Faradaic constant F = 96487 C mol-1 For a cell at its standard state, DGo = -nFEo The dimensions of Eo and DGo are V and J mol-1,Problem: Calculate the standard Gi
9、bbs function change of the reaction in the cell composed of a standard hydrogen electrode and a standard Cd electrode.,Solution: From the handbook, the electrode potentials of the two standard electrodes are known as follows, jo(Cd2+/Cd) = -0.4030 V, j(H+/H2) = 0.0000 V These electrodes can be used
10、to construct a cell with the following structure, (-)Cd|Cd2+(1 mol dm-3) | H+(1 mol dm-3) |H2(101.325kPa)| Pt(+) The cell reaction can be written as follows, Cd(s) + H+(aq) = Cd2+(aq) + H2(g) Thus, Eo = j(H+/H2) - jo(Cd2+/Cd) = 0.4030 V DGo(298.15K) = -nFEo = -2 96487 C mol-1 0.4030 V = -77770 J mol
11、-1 = 77.77 kJ mol-1,化学反应自发性的判据,如果是一个氧化还原反应，可将吉布斯函数变G 对化学反应自发性的判据转化成由E进行判断： G 0 反应可自发进行； G = 0时，E = 0 系统处于平衡状态； G 0时，E 0 逆反应可自发进行。 标准平衡常数K 的电化学测定,lgK =,通过测量原电池的标准电动势E，就可计算电池反应在任何温度T下的标准平衡常数K,6.2.2 电极和电极电势,1电极及电极反应,原电池由两个半电池组成，每个半电池都是由同一元素的氧化态物质和还原态物质组成的,Overall reaction: Zn(s) + Cu2+(aq) = Zn2+(aq) +
12、 Cu(s) Oxidation reaction: Zn(s) 2 e- = Zn2+(aq) at anode (negative terminal) Reduction reaction: Cu2+(aq) + 2 e- = Cu(s) at cathode (positive terminal),Half reaction: A cell reaction can be considered to be composed of two parts, one is the oxidation reaction occurring at anode, and the other is th
13、e reduction reaction at cathode. Each of them is called a half reaction,Oxidized state + z e-,Reducing state,reduction,oxidation,redox couple, oxidized state/reducing state Cu2+ / Cu , Zn2+/ Zn,氧化还原电对,同一元素的氧化态物质和还原态物质,电极反应（electrode reaction）：氧化态 + z e 还原态,半电池就是一个电极。任何一个原电池都是由两个电极构成的,表6-1 电极类型,惰性电极,
14、2.电极电势 Electrode potential,Where does the driving force come from? The fact that a primary cell can generate electric current indicates that there is a potential drop between the two electrodes, and further that each of the electrodes possesses its own electrode potential 简单地说，金属的溶解和沉积导致在金属表面与附近的薄层溶
15、液之间形成了类似于电容器一样的双电层，使得金属与金溶液间存在一个电势差，这个电势差叫做金属电极的电极电势，以符号表示， 如(Zn2+/Zn)、(Cu2+/Cu) 不同的电极有不同的电极电势。,电极电势的产生,溶解,沉积,M (s) + m H2O( l ),M(H2O)mn+ + ne -,双电势,电极电势的测量参比电极,It is yet difficult to measure the exact value of the potential of an electrode. But its relative value is satisfactory for all the purpos
16、es. To measure a relative electrode potential requires a scale standard, the electrode potential of which is arbitrarily assigned to be zero Standard electrode: standard hydrogen electrode Pt |H2(g, p=po=101.325kPa)|HCl(aq, c=1 mol kg-1, g=1) Pt |H2(101.325kPa)|H+(1 mol dm-3) jo(H+/H2) = 0.0000 V at any temperature,Figure 4.2 Schematic diagram of hydrogen electrode,Standard hydrog
