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Problem 52c
For each of the following reactions, write a balanced equation, calculate the standard emf, calculate ∆G° at 298 K, and calculate the equilibrium constant K at 298 K. (c) In basic solution, Cr1OH231s2 is oxidized to CrO42-1aq2 by ClO-1aq2.
- If the equilibrium constant for a two-electron redox reaction at 298 K is 1.5 * 10⁻⁴, calculate the corresponding ∆G° and E°.
Problem 53
- If the equilibrium constant for a one-electron redox reaction at 298 K is 8.7 * 10^4, calculate the corresponding ∆G° and E°.
Problem 54
Problem 55
Using the standard reduction potentials listed in Appendix E, calculate the equilibrium constant for each of the following reactions at 298 K:
(a) Fe(s) + Ni2+(aq) → Fe2+(aq) + Ni(s)
(b) Co(s) + 2 H+(aq) → Co2+(aq) + H2(g)
(c) 10 Br-(aq) + 2 MnO4-(aq) + 16 H+(aq) → 2 Mn2+(aq) + 8 H2O(l) + 5 Br2(l)
- Using the standard reduction potentials listed in Appendix E, calculate the equilibrium constant for each of the following reactions at 298 K: (a) Cu(s) + 2 Ag+(aq) → Cu2+(aq) + 2 Ag(s) (b) 3 Ce4+(aq) + Bi(s) + H2O(l) → 3 Ce3+(aq) + BiO+(aq) + 2 H+(aq) (c) N2H5+(aq) + 4 Fe(CN)6^3- (aq) → N2(g) + 5 H+(aq) + 4 Fe(CN)6^4-(aq)
Problem 56
Problem 57a
A cell has a standard cell potential of +0.177 V at 298 K. What is the value of the equilibrium constant for the reaction
(a) if n = 1?
Problem 57b,c
A cell has a standard cell potential of +0.177 V at 298 K. What is the value of the equilibrium constant for the reaction (b) if n = 2? (c) if n = 3?
Problem 58
At 298 K a cell reaction has a standard cell potential of +0.17 V. The equilibrium constant for the reaction is 5.5 × 105. What is the value of n for the reaction?
- A voltaic cell is based on the reaction Sn(s) + I2(s) → Sn2+(aq) + 2 I-(aq). Under standard conditions, what is the maximum electrical work, in joules, that the cell can accomplish if 75.0 g of Sn is consumed?
Problem 59
- (a) In the Nernst equation, what is the numerical value of the reaction quotient, Q, under standard conditions? (b) Can the Nernst equation be used at temperatures other than room temperature?
Problem 61
- A voltaic cell is constructed with all reactants and products in their standard states. Will the concentration of the reactants increase, decrease, or remain the same as the cell operates?
Problem 62
Problem 64
A voltaic cell utilizes the following reaction: Al1s2 + 3 Ag+1aq2 ¡ Al3+1aq2 + 3 Ag1s2 What is the effect on the cell emf of each of the following changes? (a) Water is added to the anode half-cell, diluting the solution.
Problem 65b,c
A voltaic cell is constructed that uses the following reaction and operates at 298 K: Zn(s) + Ni2+(aq) → Zn2+(aq) + Ni(s) (b) What is the emf of this cell when [Ni2+] = 3.00 M and [Zn2+] = 0.100 M? (c) What is the emf of the cell when [Ni2+] = 0.200 M and [Zn2+] = 0.900 M?
- A voltaic cell utilizes the following reaction and operates at 298 K: 3 Ce⁴⁺(aq) + Cr(s) → 3 Ce³⁺(aq) + Cr³⁺(aq) (b) What is the emf of this cell when [Ce⁴⁺] = 3.0 M, [Ce³⁺] = 0.10 M, and [Cr³⁺] = 0.010 M? (c) What is the emf of the cell when [Ce⁴⁺] = 0.010 M, [Ce³⁺] = 2.0 M, and [Cr³⁺] = 1.5 M?
Problem 66
Problem 67a
A voltaic cell utilizes the following reaction: 4 Fe2+1aq2 + O21g2 + 4 H+1aq2 ¡ 4 Fe3+1aq2 + 2 H2O1l2 (a) What is the emf of this cell under standard conditions?
Problem 67b
A voltaic cell utilizes the following reaction: 4 Fe2+1aq2 + O21g2 + 4 H+1aq2 ¡ 4 Fe3+1aq2 + 2 H2O1l2 (b) What is the emf of this cell when 3Fe2+4 = 1.3 M, 3Fe3+4= 0.010 M, PO2 = 0.50 atm, and the pH of the solution in the cathode half-cell is 3.50?
Problem 68a
A voltaic cell utilizes the following reaction: 2 Fe3+1aq2 + H21g2 ¡ 2 Fe2+1aq2 + 2 H+1aq2 (a) What is the emf of this cell under standard conditions?
Problem 68b
A voltaic cell utilizes the following reaction: (b) What is the emf for this cell when 3Fe3+4 = 3.50 M, PH2= 0.95 atm, 3Fe2+4 = 0.0010 M, and the pH in both half-cells is 4.00?
- A voltaic cell is constructed with two Zn²⁺/Zn electrodes. The two half-cells have [Zn²⁺] = 1.8 M and [Zn²⁺] = 1.00 × 10⁻² M, respectively. (a) Which electrode is the anode of the cell? (b) What is the standard emf of the cell? (c) What is the cell emf for the concentrations given? (d) For each electrode, predict whether [Zn²⁺] will increase, decrease, or stay the same as the cell operates.
Problem 69
- A voltaic cell is constructed that is based on the following reaction: Sn2+(aq) + Pb(s) → Sn(s) + Pb2+(aq) (b) If the anode half-cell contains SO4^2- = 1.00 M in equilibrium with PbSO4(s), what is the Ksp of PbSO4?
Problem 72
Problem 72a
A voltaic cell is constructed that is based on the following reaction: Sn2+(aq) + Pb(s) → Sn(s) + Pb2+(aq) (a) If the concentration of Sn2+ in the cathode half-cell is 1.00 M and the cell generates an emf of +0.22 V, what is the concentration of Pb2+ in the anode half-cell?
Problem 73a
During a period of discharge of a lead–acid battery, 402 g of Pb from the anode is converted into PbSO4(s). (a) What mass of PbO2(s) is reduced at the cathode during this same period?
Problem 73b
During a period of discharge of a lead–acid battery, 402 g of Pb from the anode is converted into PbSO4(s). (b) How many coulombs of electrical charge are transferred from Pb to PbO2?
Problem 74a
During the discharge of an alkaline battery, 4.50 g of Zn is consumed at the anode of the battery. (a) What mass of MnO2 is reduced at the cathode during this discharge?
Problem 74b
During the discharge of an alkaline battery, 4.50 g of Zn is consumed at the anode of the battery. (b) How many coulombs of electrical charge are transferred from Zn to MnO2?
- Heart pacemakers are often powered by lithium–silver chromate “button” batteries. The overall cell reaction is 2 Li(s) + Ag2CrO4(s) → Li2CrO4(s) + 2 Ag(s). Calculate the emf that would be generated at body temperature, 37 °C. How does this compare to the emf you calculated in part (b)?
Problem 75
Problem 75a
Heart pacemakers are often powered by lithium–silver chromate 'button' batteries. The overall cell reaction is 2 Li(s) + Ag2CrO4(s) → Li2CrO4(s) + 2 Ag(s) (a) Lithium metal is the reactant at one of the electrodes of the battery. Is it the anode or the cathode?
Problem 75b
Heart pacemakers are often powered by lithium–silver chromate 'button' batteries. The overall cell reaction is 2 Li(s) + Ag2CrO4(s) → Li2CrO4(s) + 2 Ag(s) (b) Choose the two half-reactions from Appendix E that most closely approximate the reactions that occur in the battery. What standard emf would be generated by a voltaic cell based on these half-reactions?
- The question is quite comprehensive but could be slightly confusing due to the presentation of chemical equations. Here is a more reader-friendly version: 'Mercuric oxide dry-cell batteries are often used where a flat discharge voltage and long life are required, such as in watches and cameras. The two half-cell reactions that occur in the battery are: 1. HgO(s) + H2O(l) + 2 e⁻ → Hg(l) + 2 OH⁻(aq) 2. Zn(s) + 2 OH⁻(aq) → ZnO(s) + H2O(l) + 2 e⁻ (b) The value of E°_red for the cathode reaction is +0.098 V. The overall cell potential is +1.35 V. Assuming that both half-cells operate under standard conditions, what is the standard reduction potential for the anode reaction?'
Problem 76
- (a) Suppose that an alkaline battery was manufactured using cadmium metal rather than zinc. What effect would this have on the cell emf?
Problem 77