Chapter11 Oxidation(氧化)and Reduction(还原) Acid-base reaction Transfer of proton Oxidation and reduction transfer of electron
Chapter 11 Oxidation (氧化) and Reduction (还原) Acid-base reaction: Transfer of proton Oxidation and reduction: transfer of electron
11. 1 Oxidation is the loss of electrons and reduction is the gain of electrons Oxidation is the process whereby a reactant oses one or more electrons Reduction is the opposite process whereby a reactant gains one or more electrons Oxidation and reduction are complementary and simultaneous processes 2Na+Cl—→2NaC 2Na -+2Na+ 2e Oxidation CI2+ 2e 2CI- Reduction In this reaction sodium is acting as a reducing agent(还原剂), which is any reactant that causes another reactant to be Fig 11.1 formation of sodium reduced. Conversely, the chlorine causes chloride oxidation of the sodium and so it is acting as an oxidizing agent(氧化剂)
11.1 Oxidation is the loss of electrons and reduction is the gain of electrons • Oxidation is the process whereby a reactant loses one or more electrons. • Reduction is the opposite process whereby a reactant gains one or more electrons. • Oxidation and reduction are complementary and simultaneous processes. • 2Na + Cl2 2NaCl • 2Na 2Na+ + 2e- Oxidation • Cl2 + 2e- 2Cl- Reduction • In this reaction, sodium is acting as a reducing agent (还原剂), which is any reactant that causes another reactant to be reduced. Conversely, the chlorine causes oxidation of the sodium and so it is acting as an oxidizing agent （氧化剂）. Fig 11.1 formation of sodium chloride
Different elements have different oxidation and reduction tendencies Little tendency to lose or Tendency gaIn electrons Na Mg to gal electrons Cr MnI Fe Co Ni CulZn G Tendency to lose Ru Rh Pd Ag cd In sb electrons Rel Os Bi Po At Rn Is Hs M1 110 5606162636416566167 Ce Pr Pm sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am cm Bk cr Es Fm Md No
Different elements have different oxidation and reduction tendencies Little tendency to lose or gain electrons Tendency to gain electrons Tendency to lose electrons
11.2 Photography works by selective oxidation and reduction ( Te Sim is exposed. The film is developed Camera len Light-tight Hydroquinone solution(C,) Microcrystal Oxdation Br Oxidation 2C6HgO2 2CgH4O+2e +2H Reduction Ag + e Reduction 2 Ag Br + 2e 2Ag +2 Br ③ The is fixed and washed. The negative is dark where Ag"ions have Light projected through the negative is capture orographic paper as a positive image (Na25yO,l followe Figure 11.4 Black-and-white photography involves a series of oxidation-reduction reactions
11.2 Photography works by selective oxidation and reduction
11.3 The energy of flowing electrons can be harnessed Electrochemistry(电 valuatcler 化学) is the study of CTk→ the relationship Salt bridge between electrical energy and Ceder 2n-t chemical change ZnsO, solut Cuso soleiun Use oxidation reduction reaction to produce an electric current or use an electric current to 2e+ Orta-2Cun) produce an /ne)I CH"(il 141Cm( OXidation-reduction reaction Fig 11.7 the salt bridge completes the electric circuit
11.3 The energy of flowing electrons can be harnessed • Electrochemistry (电 化学) is the study of the relationship between electrical energy and chemical change: Use oxidationreduction reaction to produce an electric current or use an electric current to produce an oxidation-reduction reaction. Fig 11.7 the salt bridge completes the electric circuit
The electricity of a battery comes from oxidation- reduction reactions a voltaic cell. which is an all-in-one, self- contained unit, is called a battery. Batteries are either disposable or rechargeable Principle of batteries: Two materials that oxidize and reduce each other are connected by a medium through which ions travel to balance an external flow of electrons
• The electricity of a battery comes from oxidationreduction reactions • A voltaic cell, which is an all-in-one, selfcontained unit, is called a battery. Batteries are either disposable or rechargeable. • Principle of batteries: Two materials that oxidize and reduce each other are connected by a medium through which ions travel to balance an external flow of electrons
Disposable batteries Reduction 2NH4++2e'-+ 2NH3+H2 Electrons(e-) Fig 11.8 a common battery dry-cell battery with a Electrons (e-) (cathode) graphite rod Light bulb dload immersed in a paste of ammonium Separator chloride, manganese Carbon and dioxide mixture dioxide, and zinc chloride electrode (anode) Electrons(e-) Oxidation zn Zn2++2e Zncl2(ag)+ 2NH3(g)+Zn(NH3)2Cl2(s 2Mno2(s)+ H2(g)-+Mn2O3(s)+ H2O( Electrode(电极) cathode(阳极): Where chemicals are reduced Anode(阴极): Where chemicals are oxidized
Disposable batteries ZnCl2 (ag) + 2NH3 (g) Zn(NH3 )2Cl2 (s) 2MnO2 (s) + H2 (g) Mn2O3 (s) + H2O (l) Electrode (电极) cathode (阳极): where chemicals are reduced. Anode (阴极): where chemicals are oxidized. Fig 11.8 a common dry-cell battery with a graphite rod immersed in a paste of ammonium chloride, manganese dioxide, and zinc chloride Reduction 2NH4 ++2e- 2NH3+H2 Oxidation Zn Zn2++2e-
Alkaline battery O D8 Fig11. 19 Alkaline batteries last a lot longer than dry-cell batteries and give a steadier voltage, but they are expensive Zn(s)+2OH-(agZno(s)+H2o(+2 e-Oxidation 2Mno2(s)+ 2e--+ Mn2O3(S)+ 20H-(ag) Reduction
Alkaline battery Zn (s) + 2OH- (aq) ZnO (s) + H2O (l) +2 e- Oxidation 2MnO2 (s) + 2e- Mn2O3 (s) + 2OH- (aq) Reduction Fig11.19 Alkaline batteries last a lot longer than dry-cell batteries and give a steadier voltage, but they are expensive
Rechargeable battery engine Fig 11.10(a)electrical energy from the battery forces the starter motor to start the engine. (b the combustion of fuel Oxidation Pb+ SO4->PbSO4+ 2 keeps the engine Reduction of elemental Pb to pb2+ running and provides Reduction Pbo2+So4+ 4H++ 2e>PbSO4+ 2H2O energy to spin the alternator, which Oxidation of elemental pb+ to pb2 recharges the battery Note that the battery has a reversed cathode- engine anode orientation during rechargin alternator Oxidation PbSO4 +2e>Pb+ SO42 Reduction of elemental Pb+ to pb Reduction Pbso pb4+ 4+ 2H20>PbO 2+ SO4+ 4H+ 2e Oxidation of elemental pb2+ to pbat
Rechargeable battery engine Oxidation Pb + SO4 2- → PbSO4 + 2e Reduction of elemental Pb to pb2+ Reduction PbO2 + SO4- + 4H+ + 2e → PbSO4 + 2H2O Oxidation of elemental pb4+ to pb2+ engine alternator Oxidation PbSO4 + 2e → Pb + SO4 2- Reduction of elemental Pb2+ to pb Reduction PbSO pb4+ 4 + 2H2O → PbO2 + SO4 - + 4H+ + 2e Oxidation of elemental pb2+ to pb4+ Fig 11.10 (a) electrical energy from the battery forces the starter motor to start the engine. (b) the combustion of fuel keeps the engine running and provides energy to spin the alternator, which recharges the battery. Note that the battery has a reversed cathodeanode orientation during recharging
Fuel cells(燃料电池) are highly efficient sources of electrical energy Oxidation 2H,+40H- 一+4b+4 e Ful ce Reduction 4e+O2+2H2O 4oH- Electron Flow 个 Hydr 个 xygen Hydroxyl Water lons Anode Electrolyte Cathode Fig 11.11 the hydrogen Porous graphite electrodes oxygen fuel cell
Fuel cells (燃料电池) are highly efficient sources of electrical energy Oxidation 2H2+4OH- 4H2O+4e- Reduction 4e-+O2+2H2O 4OHPorous graphite electrodes Fig11.11 the hydrogenoxygen fuel cell