厦门大学：《物理化学 Physical Chemistry》课程电子教案（PPT教学课件）电化学 Electrochemistry（3）

Physical chemistry Electrochemistry (3 Xuan Cheng Xiamen University

1 Electrochemistry(3) Xuan Cheng Xiamen University Physical Chemistry

Ch ical chemistr ectrochemid四 Electrolytic Conductivity The electric current l (1646) The electric current densit (1647) The conductivity K K≡ y j=KE (1649) E The reciprocal of conductivity (resistivity)p (1650)* K

2 Physical Chemistry Electrolytic Conductivity Electrochemistry The electric current I (16.46)* dt dQ I  (16.47)* A I j  The electric current density j The conductivity  The reciprocal of conductivity (resistivity)  (16.50)*   1  (16.49)* E j   j = E

Ch ical chemistr ectrochemid四 Electrolytic Conductivity The resistance R Rs/4/ (1646)* R ohm (1654) The conductance G A 电导G=x4长度= G=K 面积=A 1s=1g1 单位立方体 Siemens mho 电导率x 电导率的定义

3 Physical Chemistry Electrolytic Conductivity l A G =  The resistance R (16.46)* I R |  |  A l R  = (16.54) The conductance G 1 S=1 -1 Siemens  ohm -1 mho Electrochemistry

Ch ical chemistr ectrochemid四 Molar Conductivity The conductivity of a solution -k I mol depends on the number of ions present The molar conductivity Am 单位间距 单位立方体 K 单位面积 电导率x (1658) (b) C 摩尔电导率的定义 The electrolyte s stoichiometric molar concentration

4 Physical Chemistry Molar Conductivity The conductivity of a solution depends on the number of ions present The molar conductivity m c m    Electrochemistry (16.58)* c m    The electrolyte’s stoichiometric molar concentration

choical Chemistry Elcctrochemiary Molar Conductivity K KVs。C (1658)* HoSO Strong electrolytes H2SO4 KOH Fully ionized in solution: ionic KCI KOH solids, strong acids and bases The concentration of ions is proportional to the concentration of electrolyte added OA CHCOOI 0 10 Weak electrolytes MgSO CH, COOH c/(mol-dm Neutral electrolytes KCl Conductivity Vs. concentration

5 Physical Chemistry H2SO4 KOH KCl MgSO4 CH3COOH 0 5 15 10 c/(moldm-3 ) 20 40 60 80 Conductivity vs. concentration k/( Sm-1 ) 0  vs. c Strong electrolytes Fully ionized in solution: ionic solids, strong acids and bases The concentration of ions is proportional to the concentration of electrolyte added Weak electrolytes MgSO4 CH3COOH Neutral electrolytes KCl H2SO4 KOH Molar Conductivity Electrochemistry (16.58)* c m   

80 H2SO4 60 KOH KCI E40 20 MESO4 0 0 1015 c/(mold 3) Conductivity vs concentration

6 演示

Chical chemistr Elcctrochemiary Molar conductivity In an extensive series of measurements during 19th century, Friedrich Kohlrausch The limiting molar conductivity At low concentrations 400 A=A-K 300 The infinite-dilute molar conductivity A++A=vn+vn 200 100 AgNO The infinite-dilute molar conductivity of the cations and anions CHCOOH Law of the independent migration of ions 0.5 1.5

7 400 300 200 100 3 B/mol dm− c  m/(Scm 2 mol -1 ) HCl NaOH AgNO3 CH3COOH 0 0.5 1.0 1.5 In an extensive series of measurements during 19th century, Friedrich Kohlrausch At low concentrations + + − −     =  + + − =  +  m m m The infinite-dilute molar conductivity K c m = m −  The infinite-dilute molar conductivity of the cations and anions Law of the independent migration of ions Molar Conductivity Physical Chemistry o m The limiting molar conductivity Electrochemistry

400 HCI 300 NOH 200 10 AgNO3 CH3COOTT 0.5 1.5旗垂 cIwol-dei 厦门大学化学化工学院

8 演示

摩尔电导率与浓度的关系 由于溶液中导电物质的量已给定,都为lmol, 所以,当浓度降低时,粒子之间相互作用减弱,正、 负离子迁移速率加快,溶液的摩尔电导率必定升高。 但不同的电解质,摩尔电导率随浓度降低而升高的 程度也大不相同

9 摩尔电导率与浓度的关系 由于溶液中导电物质的量已给定，都为1mol， 所以，当浓度降低时，粒子之间相互作用减弱，正、 负离子迁移速率加快，溶液的摩尔电导率必定升高。 但不同的电解质，摩尔电导率随浓度降低而升高的 程度也大不相同

ectrochemid四 c/(mol·dm) 0.0010.0050.010.02 0.05 0.045 H CI 0.040 0.035 0.030 sO 0.025 0.015 KCI LaCI 0.010 Na. SOa 0.005 CH:COONE CHICOOH 0.050.100.150.200.25

10 o  m Electrochemistry