第11章电化学基础 2

第11章 电化学基础 Electrochemistry foundation
11-1 Oxidation-Reduction Reaction 11-2 galvanic cells
11-3 pragmatic cells
11-4 several problem about electrolysis
Elecreochemistry is important in other less obvious ways. For example, the corrosion of iron, which has tremendous economic implication, is an electrochemical process. In addition, many important industrial materials such as aluminum, chlorine, and sodium hydroxide are prepared by electrolytic process. In analytical chemistry, electrochemical techniques employ electrodes that are specific for a given molecule or ion, including H+(pH meters), F-, Cl-, and many others. These increasingly important method are used to analyze for trace pollutants in natural water or for the tiny quantities of chemicals in human blood that may signal the development of a specific disease.
11-2-2 half-cells· symbol of galvanic cells· classification of electrode 半电池half-cells = 金属棒 + 对应的溶液 = 电极 electrode 电极反应 electrode reaction
2 、 oxidation- reduction (redox) pairs and half reaction) a redox reaction can be breaked into two half reaction. Conjugate redox pairs
共轭氧化还原电对
reduction reaction
化学反应的分类
非氧化还原反应 化 学 反 应 氧化还原反应 酸碱反应 沉淀反应（无电子的转移） 配位反应
有电子的转移（元素的 氧化数发生了变化）
11-1
Oxidation-Reduction Reaction
氧化还原→氧化—得氧，还原—失氧 ↓ 电子转移（得失 ，偏移）
An oxidation-reduction（redox）reaction involves a transfer of electrons from the reducing agent to the oxidizing agent，and that oxidation involves a loss of electrons （an increase in oxidation number） and reduction involves a gain of electrons （a decrease in oxidation number）。
SO32- + H2O
SO42- + 2H+ + 2e
④合并为总离子反应式（最小公倍数） 2 MnO4- + 5 SO32- + 6H+ ⑤完善为分子式（不引入杂质） 2KMnO4 + 5K2SO3 + 3H2O 2MnSO4 + 6K2SO4 + 3H2O 2Mn2+ + 5 SO42 - + 3H2O
MnO4- + 8H+ + 5eMn2+ +4H2O ① MnO4- / Mn2+ 共轭 氧化 还原 电对 Conjugate redox pairs
oxidation reaction
+ 5( Fe2+ Fe3+ + e ) ② Fe3+ / Fe2+
The balanced overall reaction is the sum of the half-reaction
③盐桥作用 // contact
3、analysis Zn棒 e-
Zn2+(aq)
金属导线
铜棒
Cu2+(aq) +2 e-
铜析出
ZnSO4 + Zn2+ 带正电荷
盐桥（KCl）： Cl- ↑
CuSO4 + SO42-Fra bibliotek带负电荷
K+↑ 溶液保持电中性
Result is that the species(Zn) is completely dissolved in solution, but Cu2+ is completely changed to Cu and precipitating down.
A survey about electrochemistry
Elecreochemistry constitutes one of the most important interfaces between chemistry and everyday life. Every time you start your car, turn on your light and calculator, look at digital watch, or listen to a radio at the room, you are depending on electrochemical reaction. Our society sometimes seems to run almost entirely on batteries. Certainly, the advent of small, dependable batteries along with silicon chip technology has made possible the tiny calculator, hand-telephone, and robot.
MnO4- + 5Fe2+ +
8H +
=
Mn2+ + 5Fe3+ + 4H2O
共轭氧化型I + 共轭还合原型II
= 共轭还原型I + 共轭氧化型 II
1—2
Balancing oxidation- reduction equation
（一）氧化态法
1、配平原则： ① 氧化态降低总数 = 还原剂氧化态升高总数 ② 质量守恒 2、具体步骤：（1）（2）（3）（4）P360 由于反应大都是在一定的酸碱性介质中进行的，因此H+、OH和H2O在氧化还原反应中是十分重要的。 例11-1，11-2 （二）离子—电子法
. ● Electrochemistry is best defined as the study of the
interchange of chemical and electrical energy.
● It is primarily concerned with two processes that
11-1-2 half reaction of oxidation- reduction
一、Basic concept 1、oxidant（ oxidizing agent ）—失去电子的物质，电子 的给予体、反应中氧化数升高
reductant（ reducing agent ）— 得到电子的物质，电子
的接受体、反应中氧化数降低
MnO4- + 5Fe2+ + 8H + 氧化还原 Mn2+ + 5Fe3+ + 4H2O e oxidant1 reductant 2 reductant1 oxidant2
Note that MnO4- and Fe2+ are present in the same solution，the electrons are transferred directly as the reactant collide. Under these conditions no useful work is obtained from the chemical energy associated with the reaction, which instead is released as heat. How can we harness this energy ? The key is to separate the oxidizing agent from the reducing agent,.
1—1 Oxidation state（氧化态）
Oxidation number (氧化数)
一、Oxidation state（氧化态）
1、definition： Oxidation state(number)是元素一个原子的 形式电荷，这种形式电荷是由假设两个键中的电子指定给电负 性更大的原子而求得（以化合价为基础）。 2、rule：①单质中元素的氧化数为零,离子Xn-氧化数为n-。
1、写出主要反应物和产物
2、写出两个半反应 3、配平两个半反应（质量守恒，电荷平衡） 4、最小公倍数→半反应合成总反应