页数：49页文件大小：1.50 MB来源： Atkins’PhysChem物理化学ppt课件
本课件讲电动势的实际应用：用电池测定 pH 与 pKa，由电动势的温度系数求反应的熵变与焓变，并通过标准电动势计算平衡常数与溶剂化吉布斯自由能，把电化学与热力学贯通起来。
Thermodynamic functions of ions in solution Electrochemical cell Half - reactions and electrodes Thermodynamic functions of formation I on activities Varieties of cell Standard potentials Applications of standard potential The electrochemical series The meas
标准电极电势
In galvanic cell, the overall cell potential is contributed by each of the electrode. We cannot measure the contribution of a single electrode, but we can define the potential of one of the electrode as zero and then assign values to others on that basis.
10.5 Standard potentials The specially selected electrode is the stand
The standard potential, E , of another couple is then assigned by conducting as the right - hand electrode and the SHE as the left - hand electrode in the cell. 10.5 Standard potentials For example: the standard potential of the A
The standard potential of the AgCl / A g, Cl couple is the standard emfof the following cell: 10.5 Standard potentials Although we write: AgCl (s) + e - A g (s) +
The important feature of standard emfofcell and standard potential of the electrodes: They are unchanged if the chemical reaction for the cell reaction or half - reaction is multiplied by a numerical factor. 10.5 Standard potentials 6 E = - ∆ G / ν F
The standard emf of a cell can be calculated by the difference of the standard potentials of the two electrodes. (a) The cell emf in terms of individual Standard potentials Consider:
(b) The measurement of standard potentials The standard potential of o
(b) The measurement of standard potentials Example: the standard poten
(b) The measurement of standard potentials Using the molality and the
(b) The measurement of standard potentials the plot of E + (2 RT / F
平衡电化学 例题
Example: Devise a cell in which the cell reaction isMg (s) + Cl 2 (g) → MgCl 2 (a q). Give the half - reactions for the electrodes and from the standard cellemf of 3.00 V deduce the standard potential of theM g 2 + / Mg couple.
Solution: the above reaction indicates that Cl 2 gas is reduced and Mg is oxidized. (b) The measurement of standard potentials Right: Cl 2 (g) + 2 e - → 2
(b) The measurement of standard potentials Cell reaction: 2 Fe 3 + (a
平衡电化学 例题
Example: Consider a hydrogen electrode in aqueous HCl solution at 25 º C operating at 105 kPa. Calculate the change in the electrode potential when the molality of the acid is changed from 5.0 mmolkg - 1 to 50 mmolkg - 1.
Activity coefficient can be found from At k in’ s textbook (Table 10.5). (b) The measurement of standard potentials Solution: H + (a q) + e - →
(c) The measurement of activity coefficients Once the standard potenti
10.6 The electrochemical series For two redox couples O x 1 / Red 1 an
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10.7 Measuring pH or pKa The half reaction at a hydrogen electrode: H
10.7 Measuring pH or pKa The potential of a single electrode cannot be
10.7 Measuring pH or pKa The right - hand electrode is hydrogen electr
10.7 Measuring pH or pKaWhereE is the emf of the cell: Pt (s) | H 2 (g
10.7 Measuring pH or pKaA saturated aqueous solution of potassium hydr
10.7 Measuring pH or pKaIt is filled with a phosphate buffer containin
10.7 Measuring pH or pKaTheH + ions in the test solution modify the la
10.7 Measuring pH or pKa Electrodes can be constructed with potentials
10.8 Thermodynamic function Nernst equation is the bridge to the conne
10.8 Thermodynamic function Solution: First, write down the cell react
10.8 Thermodynamic function Consider: Pt (s) | H 2 (g) | H + (a q) | A
Temperature dependence of emfdE / dTis called temperature coefficien
Temperature dependence of emf This expression provides an electrochemi
Temperature dependence of emfwas measured over a broad range of temper
Temperature dependence of emfAt 298 K, E / V = 0.07, E = 0.07 V So
Temperature dependence of emf Calculate the temperature coefficient of
Temperature dependence of emfWas found to be + 0.269 V at 293 K and +
Temperature dependence of emfE = 0.2675 V; Δ r G = - 2 FE = - 51
Evaluate the reaction potential from two others Solution: First write
Evaluate the reaction potential from two others Reaction 3 is the sum
Evaluate the reaction potential from two others Solution: Again, we sh
Evaluate the reaction potential from two others - 1 F E (C u 2 +
Exercises Exercises (a) 10.25, 28, 30, 32 Discussion: problem 10.449
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