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- What products should be formed when the following reac-tants are electrolyzed in a cell having inert electrodes? Account for any differences. (b) Aqueous KCl
Problem 135
Problem 136b
Predict the anode, cathode, and overall cell reactions when an aqueous solution of each of the following salts is electrolyzed in a cell having inert electrodes. (b) CuCl2
Problem 136c
Predict the anode, cathode, and overall cell reactions when an aqueous solution of each of the following salts is electrolyzed in a cell having inert electrodes. (c) LiOH
- Predict the anode, cathode, and overall cell reactions when an aqueous solution of each of the following salts is electrolyzed in a cell having inert electrodes. (a) Ag2SO4
Problem 137
- How many hours are required to produce 1.00 * 103 kg of sodium by the electrolysis of molten NaCl with a constant current of 3.00 * 104 A? How many liters of Cl2 at STP will be obtained as a by-product?
Problem 140
- What constant current (in amperes) is required to produce aluminum by the Hall–Héroult process at a rate of 40.0 kg/h?
Problem 141
- Electrolysis of a metal nitrate solution M(NO3)2(aq) for 325 min with a constant current of 20.0 A gives 111 g of the metal. Identify the metal ion M2+.
Problem 142
- Aluminum, titanium, and several other metals can be col-ored by an electrochemical process called anodizing. Anodizing oxidizes a metal anode to yield a porous metal oxide coating that can incorporate dye molecules to give brilliant colors. In the oxidation of aluminum, for instance, the electrode reactions are The thickness of the aluminum oxide coating that forms on the anode can be controlled by varying the current flow during the electrolysis. How many minutes are required to produce a 0.0100-mm thick coating of Al2O3 (density 3.97 g/cm^3) on a square piece of aluminum metal 10.0 cm on an edge if the current passed through the piece is 0.600 A?
Problem 144
Problem 146a
In order to charge a lead storage battery (Section 19.10) 500.0 g of PbSO4(s) must be converted into PbO2(s) and Pb(s). (a) Does the reaction represent an electrolytic or galvanic cell?
Problem 146b
In order to charge a lead storage battery (Section 19.10) 500.0 g of PbSO4(s) must be converted into PbO2(s) and Pb(s). (b) How many coulombs of electrical charge are needed?
Problem 146c
In order to charge a lead storage battery (Section 19.10) 500.0 g of PbSO4(s) must be converted into PbO2(s) and Pb(s). (c) If a current of 500 A is used, how long will it take?
Problem 147a
When the nickel–zinc battery, used in digital cameras, is recharged, the following cell reaction occurs: (a) How many grams of zinc are formed when 3.35 x 10-2 g of Ni(OH)2 are consumed?
- Consider the following half-reactions and E° values: (c) Write the cell reaction for part (b), and calculate the values of E°, ∆G° (in kilojoules), and K for this reaction at 25 °C
Problem 148
- Chlorine can be prepared in the laboratory by the reaction of hydrochloric acid and potassium permanganate. (b) Calculate E° and ∆G° for the reaction
Problem 150
Problem 150a
Chlorine can be prepared in the laboratory by the reaction of hydrochloric acid and potassium permanganate. (a) Use data in Appendix D to write a balanced equation for the reaction. The reduction product is Mn2+.
- The sodium–sulfur battery has molybdenum electrodes with anode and cathode compartments separated by b-alumina, a ceramic through which sodium ions can pass. Because the battery operates at temperatures above 300 °C, all the reactants and products are present in a molten solution. The cell voltage is about 2.0 V. (b) How many kilograms of sodium are consumed when a 25 kW sodium–sulfur battery produces current for 32 min?
Problem 151
- A galvanic cell has a silver electrode in contact with 0.050 M AgNO3 and a copper electrode in contact with 1.0 M Cu(NO3)2. (a) Write a balanced equation for the cell reaction, and calculate the cell potential at 25 °C.
Problem 153
Problem 154
Given the following standard reduction potentials at 25 °C, (a) balance the equation for the reaction of H2MoO4 with elemental arsenic in acidic solution to give Mo3+ and H3AsO4 and (b) calculate E° for this reaction.
Problem 155a
The reaction of MnO4– with oxalic acid (H2C2O4) in acidic solution, yielding Mn2+ and CO2 gas, is widely used to determine the concentration of permanganate solutions. (a) Write a balanced net ionic equation for the reaction.
Problem 155b,c
The reaction of MnO4– with oxalic acid (H2C2O4) in acidic solution, yielding Mn2+ and CO2 gas, is widely used to determine the concentration of permanganate solutions. (b) Use the data in Appendix D to calculate E° for the reaction. (c) Show that the reaction goes to completion by calculating the values of ∆G° and K at 25 °C. (H2C2O4) in acidic solution, yielding Mn2+ and CO2 gas, is widely used to determine the concentration of permanganate solutions.
Problem 155d
The reaction of MnO4– with oxalic acid (H2C2O4) in acidic solution, yielding Mn2+ and CO2 gas, is widely used to determine the concentration of permanganate solutions. (d) A 1.200 g sample of sodium oxalate (Na2C2O4) is dissolved in dilute H2SO4 and then titrated with a KMnO4 solution. If 32.50 mL of the KMnO4 solution is required to reach the equivalence point, what is the molarity of the KMnO4 solution?
- Calculate the standard reduction potential for Ba2+ (aq) + 2 e- -> Ba(s) given that ∆G° = 16.7 kJ for the reaction Ba2+(aq) + 2Cl-(aq) -> BaCl2(s). Use any necessary data from Appendices B and D.
Problem 156
- A concentration cell has the same half-reactions at the anode and cathode, but a voltage results from different concentrations in the two electrode compartments. (b) A similar cell has 0.10 M Cu2+ in both compartments. When a stoichiometric amount of ethylenediamine (NH2CH2CH2NH2) is added to one compartment, the measured cell potential is 0.179 V. Calculate the formation constant Kf for the complex ion Cu(NH2CH2CH2CH2)22+. Assume there is no volume change.
Problem 157
Problem 158a
Consider the redox titration (Section 4.13) of 120.0 mL of 0.100 M FeSO4 with 0.120 M K2Cr2O7 at 25 °C, assuming that the pH of the solution is maintained at 2.00 with a suitable buffer. The solution is in contact with a platinum electrode and constitutes one half-cell of an electrochemical cell. The other half-cell is a standard hydrogen electrode. The two half-cells are connected with a wire and a salt bridge, and the progress of the titration is monitored by measuring the cell potential with a voltmeter. (a) Write a balanced net ionic equation for the titration reaction, assuming that the products are Fe3+ and Cr3+.
- Consider a galvanic cell that utilizes the following half-reactions:
Problem 159
(b) What are the values of E° and the equilibrium constant K for the cell reaction at 25 °C? - The nickel–iron battery has an iron anode, an NiO(OH) cathode, and a KOH electrolyte. This battery uses the follow-ing half-reactions and has an E° value of 1.37 V at 25 °C. (b) Calculate ∆G° (in kilojoules) and the equilibrium con-stant K for the cell reaction at 25 °C.
Problem 160
Problem 161b
Experimental solid-oxide fuel cells that use butane (C4H10) as the fuel have been reported recently. These cells contain composite metal/metal oxide electrodes and a solid metal oxide electrolyte. The cell half-reactions are (b) Use the thermodynamic data in Appendix B to calculate the values of E° and the equilibrium constant K for the cell reaction at 25 °C. Will E° and K increase, decrease, or remain the same on raising the temperature?
Problem 161c
Experimental solid-oxide fuel cells that use butane (C4H10) as the fuel have been reported recently. These cells contain composite metal/metal oxide electrodes and a solid metal oxide electrolyte. The cell half-reactions are (c) How many grams of butane are required to produce a constant current of 10.5 A for 8.00 h? How many liters of gaseous butane at 20 °C and 815 mm Hg pressure are required?
Problem 162a
The half-reactions that occur in ordinary alkaline batteries can be written as In 1999, researchers in Israel reported a new type of alkaline battery, called a 'super-iron' battery. This battery uses the same anode reaction as an ordinary alkaline battery but involves the reduction of FeO42- ion (from K2FeO4) to solid Fe(OH)3 at the cathode. (a) Use the following standard reduction potential and any data from Appendixes C and D to calculate the standard cell potential expected for an ordinary alkaline battery:
Problem 162b
The half-reactions that occur in ordinary alkaline batteries can be written as In 1999, researchers in Israel reported a new type of alkaline battery, called a 'super-iron' battery. This battery uses the same anode reaction as an ordinary alkaline battery but involves the reduction of FeO42- ion (from K2FeO4) to solid Fe(OH)3 at the cathode. (b) Write a balanced equation for the cathode half-reaction in a super-iron battery. The half-reaction occurs in a basic environment.