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1、第四章 电化学基础（The fourth chapter is electrochemical basis）The fourth chapter is electrochemical basisSection 1 primary cell1, the concept of chemical energy into electrical energy device called primary battery _2. Composition conditions: two electrodes with different activity, electrolyte solution, elec
2、trodes connected by wire and inserted into electrolyte to form closed loop3 、 electronic flow direction: external circuit: negative electrode - lead wire - positive electrodeIn the circuit: move to the salt bridge anion in electrolyte solution of the negative electrode in electrolyte solution to cat
3、ionic saltbridge cathode.4 electrode reaction: a case study of zinc copper galvanic cell:Negative: oxidation: Zn2e = Zn2 + (active metal)Cathode reduction reaction: = H2 = 2H2e (less active metal)The total reaction type: Zn+2H+=Zn2+H2 =5, positive and negative judgments:(1) from the electrode materi
4、al: generally more active metal as negative electrode; or metal as negative electrode, non metal as positive electrode.(2) from the direction of the electron flow, the negative electrode flows into the positive electrode(3) the anode flows from the current direction to the negative electrode(4) the
5、cation flows to the positive electrode according to the direction of the ion movement in the electrolyte solution, and the anion flows to the negative electrode(5) according to the experimental phenomena of _ dissolved a negative _ II weight or have a positive bubbleSecond chemical batteries1. Class
6、ification of batteries: chemical batteries, solar cells, atomic energy batteries2. Chemical battery: a device that converts electricity directly into electrical energy by chemical energy3. Classification of chemical batteries: primary batteries, two batteries, fuel cellsI. primary batteries: common
7、primary batteries: alkaline zinc manganese batteries, zinc silver batteries, lithium batteries, etc.Two and two batteries1 and two batteries: after discharge can be recharged, so that active substances are recycled, can be reused several times, also known as rechargeable batteries or batteries.2 ele
8、ctrode reaction: lead storage batteryDischarge: negative (PB): Pb2e = PbSO4 down?Positive (PBO): PbO24H+2e = PbSO4: 2H2O?Charging: cathode: PbSO42H2O2e = PbO24H+?Anode: PbSO42e = Pb?The type two can be written as a reversible reaction: PbO2 + Pb + 2H2SO4 + 2PbSO4: 2H2O3, at present, has developed a
9、new type of battery: silver zinc batteries, nickel cadmium batteries, nickel hydrogen batteries, lithium ion battery, polymer lithium ion batteryThree fuel cells1 fuel cells: a galvanic cell that reacts directly with fuel to produce an electric current2. Electrode reaction: the final product of elec
10、trochemical reaction in common fuel cell is the same as that of combustion product. The total battery reaction can be written according to the combustion reaction, but the reaction condition is not indicated. The negative electrode is oxidized and the positive electrode undergoes a reduction reactio
11、n. However, attention should be paid to the general electrolyte solution to participate in the electrode reaction. Taking hydrogen oxygen fuel cell as an example, platinum is positive and negative, and the medium is divided into acid, alkaline and neutral.When the acidic electrolyte solution: negati
12、ve: 2H24e? =4H+: e 4H+ =2H2O O24 positive?When the electrolyte solution is alkaline: negative: 2H24OH 4E? = 4H2O: e = 4OH negative O22H2O4?Another type of fuel cell is a metal platinum plate inserted into the KOH solution as an electrode, and at the poles, respectively, through methane, fuel and oxy
13、gen, oxidant.Electrode reaction is: negative: CH410OH8? E? = 7H2O;Positive: 4H2O2O28e Oh - = 8?.The total reaction cell type: CH42O22KOH = K2CO33H2O3, fuel cell advantages: high energy conversion rate, waste less, low operating noiseFour, waste battery treatment: RecyclingThird section electrolytic
14、cellElectrolysis principle1. Electrolytic cell: a device that converts electrical energy into chemical energy, also called an electrolytic cell2, electrolysis: the current (plus direct current) through the electrolyte solution at the anode and cathode of the redox reaction (passive, not spontaneous)
15、 process3, discharge: when the ion reaches the electrode, loses or obtains the electron, produces the oxidation-reduction reaction the process4 、 electron flow direction: (power) negative electrode - (electrolytic bath) cathode - (ion oriented motion) electrolyte solution - (electrolytic bath) anode
16、 - (power supply) positive electrode5. Electrode name and reaction:Anode: an electrode that is connected to the positive electrode of a DC power sourceCathode: an electrode that is connected to a negative electrode of a DC power source and undergoes a reduction reaction6, electrolytic CuCl2 solution
17、 electrode reaction: anode: 2Cl-2e, =Cl2 (oxidation) cathode: Cu2+2e, =Cu (reduction)The total reaction type: =Cu+Cl2 = CuCl27. Electrolysis essence: the conduction process of electrolyte solution is the electrolysis process of electrolyte solutionTo summarize the rules of writing: electrolytic ioni
18、c reaction equations:Cationic discharge order: Ag+Hg2+Fe3+Cu2+H+ (acid ionization) Pb2+Sn2+Fe2+Zn2+Al3+Mg2+Na+Ca2+K+Anion discharge sequence: inert electrode: S2-I-Br-Cl-OH-NO3-SO42- (such as oxygen ion), F- (SO32-/MnO4-OH-)When an active electrode is applied, the electrode itself dissolves and disc
19、hargesNote that we look at the electrode material is inert electrode or active electrode, if the anode material as active electrode (Fe, Cu) and other metal, while the anodic reaction as the electrode material loses electrons into ions into the solution; if the inert material, according to the order
20、 of discharge ions, according to Yang Yin also rules to write oxygen electrode reaction.The law of point product in aqueous electrolyte solutionType electrode reaction characteristics example electrolysis object electrolyte concentration pH electrolyte solution restorationThe ionization of anion and
21、 cation in the electrolyte and the HCl electrolyte decrease and increase HClCuCl2 - CuCl2Release H2 to produce alkali type cathode: water puts H2 baseAnode: electrolyte anion discharge, NaCl electrolyte and water generate new electrolyte, increase HClOxygen evolving acid cathode: electrolyte cation
22、dischargeAnode: water releases O2, acid, CuSO4, electrolyte and water to form a new electrolyte, reducing copper oxideWater electrolysis cathode: 4H+ + 4e- = = = 2H24OH-: O2 = 4e-= + anode 2H2O NaOH water water increaseH2SO4 decreaseNa2SO4 invariantThe four types of electrolytes are classified:(1) e
23、lectrolyzed water: oxygen, alkali, active metal, oxygen salts(2) electrolyte type: deoxygenated inert metal salt, hydrogen acid (except fluoride)(3) students: hydrogen alkali metal salt and hydrogen acid(4) oxygen producing acid type: acid salt of inactive metalTwo. Application of electrolysis princ
24、iple1, electrolysis of saturated salt water to make caustic soda, chlorine and hydrogen(1) the method of applying a principle of electrolysis to coating a certain metal surface with a thin layer of other metal or alloy(2) the choice of electrode and electrolyte solution:Anode coating: metal loses el
25、ectrons become ions into the solution; M ne = M n+Cathode: plated metal (plated): the metal ions in the solution are electrons, become metal atoms, and attach to the metal surfaceM n+ + ne = MElectrolyte solution: solution containing a coating of metal ions to make an electroplating solutionCopper p
26、lating reaction principle: anode (pure copper):Cu-2e-=Cu2+, cathode (plating):Cu2+2e-=Cu,Electrolyte: soluble copper salt solution, such as CuSO4 solution(3) one of the electroplating applications: Copper Refining: anode: coarse copper; cathode: pure copper electrolyte solution: copper sulfate2. Ele
27、ctrical metallurgy(1) electro Metallurgy: the extraction of metal cations from ores by reducing them from their compounds; used in smelting active metals such as sodium, magnesium, calcium, and aluminum(2): electrolysis of sodium chloride and sodium chloride before electricity, high temperature melt
28、: NaCl = = Na + + Cl-Direct current: anode: 2Na+ + 2E - 2Na: 2Cl: 2E = = cathode - = = = Cl2To summarize the rule of law: judgment of primary battery, electrolytic cell, electroplating tank(1) if there is no external power supply, there are three conditions for the primary battery. The two electrode
29、s of different active; the two wires connected to each other directly connected into the electrolyte solution; the more active metal and the electrolyte solution to the redox reaction (sometimes H+ effect and water ionization), as long as with the three conditions for primary battery.(2) if the exte
30、rnal power supply, the poles inserted in the electrolyte solution may be electrolytic cell or electroplating tank; when the cathode is made of metal anode for metal ions and metal and electrolyte solution in the same element, for electroplating baths.(3) if a plurality of single tanks are connected
31、in series with an external power supply, the device connected with the power supply is an electroplating pool with an electrolytic bath. If there is no external power supply, the active metal electrode is selected as the negative electrode (the electronic output pole) of the primary cell, and the re
32、levant device is a galvanic cell, and the other is an electroplating bath or an electrolytic cell.*To compare primary battery, electrolytic cell, electroplating tankProperty classGalvanic cell, electroplating cell, bathDefinition(device characteristic) a device that converts chemical energy into ele
33、ctrical energy and converts electrical energy into chemical energy. Electrolysis is applied to the surface of some metals and to other metalsResponse characteristics, spontaneous response, non spontaneous reaction, non spontaneous reactionThe device is characterized by no power supply, two stage mat
34、erials with different power supply, and two stage materials can be provided with different power supplyForming conditions; different poles of activityelectrolyte solutionA closed loop is formed, and the two electrode is connected with a DC power supplyThe two electrode is inserted into the electroly
35、te solutionForm a closed loop 1 coating metal power supply anode, to be plated metal negative electrode; 2 plating solution must contain coating metal ionsElectrode Name: negative electrode: more active metalPositive plate: less active metal (conductive nonmetal) anode: connected to the positive pow
36、er supplyCathode: it is connected with the negative pole of the power supply. The name is the same as the electrolysis, but it has the limited conditionAnode: must be coating metalCathode: plated partsNegative electrode: an oxidation reaction in which metals lose electronsThe positive electrode: the
37、 reduction reaction, the cation of the solution, or the oxygen to the electron (oxygen, corrosion), anode: oxidation, the anion in the solution loses electrons, or the electrode metal loses electronsCathode: a reduction reaction in which the cations in the solution yield electronsAnode: metal electr
38、ode loses electronsCathode: the cation in an electroplating solution yields electronsThe electron flows to the negative pole, to the positive power supply, to the negative pole to the cathodePower supply anode + anode with electrolytic cellThe moving cations of charged particles move toward the posi
39、tive electrode in the solutionThe anion moves toward the negative and the cation moves toward the cathodeThe anion moves to the anode with the electrolytic cellOxidation and reduction reactions occur on both polesYou can feel the original battery with electrolytic cell electrode and electronic conta
40、ct map:Anode (fail) e- positive (get) e- negative (fail) e- cathode (get)Electrochemical corrosion and protection of fourth sections of metalsElectrochemical corrosion of metals(1) metal corrosion content: (2) the nature of metal corrosion: the process of metal atoms losing electrons and being oxidi
41、zed(3) classification of metal corrosion:Chemical corrosion - corrosion caused by the direct chemical reaction of metals and the substances in contactGalvanic corrosion - galvanic reactions occur when impure metals react with electrolyte solutions. More active metals are oxidized by losing electrons
42、, which are called electrochemical corrosion.Comparison of chemical corrosion and electrochemical corrosionElectrochemical corrosion atA metal or alloy in contact with an electrolyte solution; a metal that is in direct contact with an electrolyteThe phenomenon is that a weak current produces no curr
43、entA process in which the more active metal is oxidized; a process in which metals are oxidizedThe relationship between chemical corrosion and electrochemical corrosion often occurs at the same time, but electrochemical corrosion is more common and more harmful(4) classification of electrochemical c
44、orrosion:Hydrogen evolution - hydrogen is released in the process of hydrogen corrosionConditions: the water film formed in humid air has a strong acidity (dissolved in water, such as CO2, SO2, H2S and so on)Electrode reaction: negative electrode: Fe - 2e- = Fe2+Positive: 2H+ + 2e- = H2 =The general
45、 formula: Fe = Fe2+ + 2H+ + H2 =Oxygen corrosion - the reaction process to absorb oxygenCondition: neutral or weak acid solutionElectrode reaction: negative electrode: 2Fe - 4e- = 2Fe2+Positive: O2+4e- = +2H2O = 4OH-General: 2Fe + O2, +2H2O, =2, Fe (OH) 2Ionic equation: Fe2+ + 2OH- = Fe (OH) 2The ge
46、nerated Fe (OH) 2 by O2 oxidation in air, generating Fe (OH) 3, Fe (OH) 2 + O2 + 2H2O = 4Fe (OH) 3Fe (OH) 3 takes off part of the water to produce Fe2O3, x, H2O (rust, the main component)Rule summary: the law of the speed of metal corrosion: in the same electrolyte solution, the speed of metal corro
47、sion is as follows:Corrosion caused by electrolysis principle corrosion caused by galvanic cell chemical corrosion corrosion with antiseptic measuresThe order of good and bad is as follows:Cathodic protection method of external power supply sacrificial anode protection method corrosion with general corrosion protection corrosion free without corrosion protectionTwo. Electrochemical protection of metals1, use the principle of galvanic cell to carry out electrochemical protection of me