Ch.20 - Electrochemistry

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Tro 5th Edition

Ch.20 - Electrochemistry

Problem 100

Silver can be electroplated at the cathode of an electrolysis cell by the half-reaction: Ag⁺(aq) + e^– → Ag(s) What mass of silver would plate onto the cathode if a current of 6.8 A flowed through the cell for 72 min?

Problem 101

A major source of sodium metal is the electrolysis of molten sodium chloride. What magnitude of current produces 1.0 kg of sodium metal in 1 hour?

Problem 103

Consider the reaction shown here occurring at 25 °C: A(s) + B2+(aq) → A2+(aq) + B(s). Given that ∆Gr°xn = -14.0 kJ, determine the value of Ec°ell and K for the reaction, and complete the following table for [B2+], [A2+], Q, Ecell, and ∆Grxn with initial values 1.00, 1, 1.0 * 10^-4, 3.54 * 10^-3, and 1.00 * 10^-4 respectively.

Problem 104

Consider the reaction shown here occurring at 25°C. Cr(s) + Cd²⁺(aq) → Cr²⁺(aq) + Cd(s) Determine E°_cell, K, and ∆G°_rxn for the reaction and complete the table.

[Cd²⁺] [Cr²⁺] Q E_cell 𝚫G_rxn

1.00 1.00

1.00 1.00 × 10^-5

1.00 × 10^-5 1.00

4.18 × 10^-4 1.00

Problem 105

Consider the unbalanced redox reaction: MnO4-(aq) + Zn(s) → Mn2+(aq) + Zn2+(aq). Balance the equation and determine the volume of a 0.500 M KMnO4 solution required to completely react with 2.85 g of Zn.

Problem 106

Consider the unbalanced redox reaction: Cr₂O₇^2-(aq) + Cu(s) → Cr³⁺(aq) + Cu²⁺(aq) Balance the equation and determine the volume of a 0.850 M K₂Cr₂O₇ solution required to completely react with 5.25 g of Cu.

Problem 109a

Determine whether HI can dissolve each metal sample. If it can, write a balanced chemical reaction showing how the metal dissolves in HI and determine the minimum volume of 3.5 M HI required to completely dissolve the sample. a. 2.15 g Al

Problem 109b

Problem 110

Determine if HNO₃ can dissolve each metal sample. If it can, write a balanced chemical reaction showing how the metal dissolves in HNO3 and determine the minimum volume of 6.0 M HNO3 required to completely dissolve the sample. a. 5.90 g Au b. 2.55 g Cu c. 4.83 g Sn

Problem 112

The cell potential of this electrochemical cell depends on the gold concentration in the cathode half-cell. Pt(s) | H₂(g, 1.0 atm) | H⁺(aq, 1.0 M) || Au³⁺(aq, ? M) | Au(s) What is the concentration of Au³⁺ in the solution if E_cell is 1.22 V?

Problem 113

A friend wants you to invest in a new battery she has designed that produces 24 V in a single voltaic cell. Why should you be wary of investing in such a battery?

Problem 115a

A battery relies on the oxidation of magnesium and the reduction of Cu²⁺. The initial concentrations of Mg²⁺ and Cu²⁺ are 1.0 × 10^–4 M and 1.5 M, respectively, in 1.0-liter half-cells. a. What is the initial voltage of the battery?

Problem 115b

Problem 115c

Problem 116a

A rechargeable battery is constructed based on a concentration cell constructed of two Ag/Ag⁺ half-cells. The volume of each half-cell is 2.0 L, and the concentrations of Ag⁺ in the half-cells are 1.25 M and 1.0×10^–3 M. a. How long can this battery deliver 2.5 Aof current before it goes dead?

Problem 116b

A rechargeable battery is constructed based on a concentration cell constructed of two Ag/Ag⁺ half-cells. The volume of each half-cell is 2.0 L, and the concentrations of Ag⁺ in the half-cells are 1.25 M and 1.0 × 10^–3 M. b. What mass of silver is plated onto the cathode by running at 3.5 A for 5.5 h?

Problem 116c

A rechargeable battery is constructed based on a concentration cell constructed of two Ag/Ag⁺ half-cells. The volume of each half-cell is 2.0 L, and the concentrations of Ag⁺ in the half-cells are 1.25 M and 1.0 × 10^–3 M. c. Upon recharging, how long would it take to redissolve 1.00 × 10² g of silver at a charging current of 10.0 amps?

Problem 117

If a water electrolysis cell operates at a current of 7.8 A, how long will it take to generate 25.0 L of hydrogen gas at a pressure of 25.0 atm and a temperature of 25 °C?

Problem 119

The Ksp of CuI is 1.1 * 10^-12. Find Ecell for the cell: Cu(s) | CuI(s) | I^-(aq)(1.0 M) || Cu^+(aq)(1.0 M) | Cu(s)

Problem 122a

Calculate ∆G°_rxn and K for each reaction. a. The reaction of Cr²⁺(aq) with Cr₂O₇^2–(aq) in acid solution to form Cr³⁺(aq).

Problem 122b

Calculate ∆G°_rxn and K for each reaction. b. The reaction of Cr³⁺(aq) and Cr(s) to form Cr²⁺(aq). [The electrode potential of Cr²⁺(aq) to Cr(s) is -0.91 V.]

Problem 123

The molar mass of a metal (M) is 50.9 g/mol; it forms a chloride of unknown composition. Electrolysis of a sample of the molten chloride with a current of 6.42 A for 23.6 minutes produces 1.20 g of M at the cathode. Determine the empirical formula of the chloride.

Problem 124

A metal forms the fluoride MF₃. Electrolysis of the molten fluo- ride by a current of 3.86 A for 16.2 minutes deposits 1.25 g of the metal. Calculate the molar mass of the metal.

Problem 125

A sample of impure tin of mass 0.535 g is dissolved in strong acid to give a solution of Sn²⁺. The solution is then titrated with a 0.0448 M solution of NO₃^–, which is reduced to NO(g). The equivalence point is reached upon the addition of 0.0344 L of the NO₃^– solution. Find the percent by mass of tin in the original sample, assuming that it contains no other reducing agents.

Problem 126

A 0.0251-L sample of a solution of Cu+ requires 0.0322 L of 0.129 M KMnO4 solution to reach the equivalence point. The products of the reaction are Cu2+ and Mn2+. What is the concentration of the Cu+ solution?

Problem 127

A current of 11.3 A is applied to 1.25 L of a solution of 0.552 M HBr converting some of the H⁺ to H₂(g), which bubles out of solution. What is the pH of the solution after 73 minutes?

Problem 130

To what pH should you adjust a standard hydrogen electrode to get an electrode potential of -0.122 V? (Assume that the partial pressure of hydrogen gas remains at 1 atm.)