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All Textbook Solutions for Chemistry for Engineering Students
13.62PAE13.63PAE13.64PAEUse the Internet to find electroplating companies that carry out silver plating. Popular impressions are that silver plating is mostly done for cosmetic reasons, making objects (like silverware) more attractive. Based on your Internet research, do you believe this popular impression accurately reflects the plating industry?13.66PAEIf a current of 15 A is run through an electrolysis cell for 2.0 hours, how many moles of electrons have moved?Suppose somebody in a laboratory doesn't quite turn off the current in an electrolysis cell so that 4.2 mA of current continues to flow. If the cell is then left untouched for exactly 3 weeks, how many moles of electrons have flowed through the cell in that time?If a barrel plating run uses 200.0 A for exactly 6 hours for an electroplating application at 0.30 V, how many kilowatt-hours have been used in the run? If the voltage is 0.90 V, what is the power usage (in kWh)?An electrical engineer is analyzing an electroplating run and wants to calculate the charge that has been used. She knows that the cell voltage is 0.25 V and that 10.3 kWh was expended. What was the charge? If the current of the apparatus is 3.0 A, how long was it running?In a copper plating experiment in which copper metal is deposited from a copper(ll) ion solution, the system is run for 2.6 hours at a current of 12.0 A. What mass of copper is deposited?A metallurgist wants to gold-plate a thin sheet with the following dimensions: 1.5in8.5in0.0012in . The gold plating must be 0.0020 in thick. (a) How many grams of gold (d=19.3g/cm3) are required? (b) How long will it take to plate the sheet from AuCN using a current of 7.00 A? (Assume 100% efficiency.)Tin-plated steel is used for "tin" cans. Suppose that in the production of sheets of tin-plated steel, a line at a factory operates at a current of 100.0 A for exactly 8 hours on a continuously fed sheet of unplated steel. If the electrolyte contains tin(II) ions, what is the total mass of tin that has plated out in this operation?An electrolysis cell for aluminum production operates at 5.0 V and a current of 1.0105 A. Calculate the number of kilowatt-hours of energy required to produce 1 metric ton ( 1.0103 kg) of aluminum. ( 1kWh=3.6106 J and 1J=1 C V.)If a plating line that deposits nickel (from NiCl2 solutions) operates at a voltage of 0.40 V with a current of 400.0 A and a total mass of 49.0 kg of nickel is deposited, what is the minimum number of kWh consumed in this process?13.76PAE13.77PAEA small part with a surface area of 2.62 cm2 is plated with a gold coating that is 5.00104 mm thick. The density of gold is 19.32 g cm-3. What mass of gold is in this coating? If a barrel plating run has 5000 of these parts in a single barrel, how long would the run take if the current was 15.0 A? (Gold is effectively plated from Au+(aq).)An engineer is designing a mirror for an optical system. A piece of metal that measures 1.3 cm by 0.83 cm will have a coating of rhodium plated on its surface to serve as the mirror. The rhodium thickness will be 0.00030 mm, and the electrolyte contains Rh3+ ions. If the operating current of the electrolysis is 0.10 A, how long must it be operated to obtain the desired coating? What mass of rhodium is deposited? (The density of rhodium is 12.4 g cm-3.)13.80PAE13.81PAEWhat characteristic of lithium ions makes it practical to build a semipermeable separator that allows them to flow through in a lithium-ion battery? Why would a sodium-ion battery be harder to design even if the oxidationreduction reactions were similar?Looking at Figure 13.23, describe how the operation of a lithium-ion battery does not lead to a charge build up on one side of the battery or the other. FIGURE 13.23 A diagram of the chemistry of a lithium-ion battery is shown. Lithium ions move through the separator from the anode to the cathode during the spontaneous cell reaction. When the battery is recharged, an external power source forces the ions to flow in the opposite direction, from cathode to anode.13.84PAEWhat is the role of a salt bridge in the construction of a galvanic cell?13.86PAEIf the SHE was assigned a value of 3.00 V rather than 0.00 V, what would happen to all of the values listed in the table of standard reduction potentials?13.88PAE13.89PAEA chemical engineering student is studying the effect of pH on the corrosion of iron. Ellie following data are collected: Corrosion Rate (mm/year) ph 0.03 13.00 0.06 12.00 0.16 11.00 0.22 10.00 0.25 9.00 0.25 8.00 0.25 7.00 0.25 6.00 0.25 5.00 0.27 4.00 0.37 3.00 0.38 2.80 0.63 2.80 1.00 2.80 Plot corrosion rate vs. pH. (HINT: Label the x axis with decreasing pH.) (a) How would you describe the dependence of corrosion on pH? (b) When the pH goes below 3, bubbles appear in the solution. What change takes place in the reduction half-reaction at low pH? (c) How do you explain the shape of the curve at the lowest pH? (Based on a graph in the Kirk-Otbmer Encyclopedia of Chemical Technology, 4th ed., vol 7. New York: John Wiley & Sons, p. 559.)13.91PAEIf a logarithmic scale had not been used for the graph of Figure 13.13, what would the plots look like? FIGURE 13.13 The variation of equilibrium constant with cell potential is shown. The different lines correspond to reactions involving the transfer of one, two, or three electrons, as indicated.Battery manufacturers often assess batteries in terms of their specific energy (or energy capacity). The weight capacity of a battery is defined as qV/mass . Why would a battery manufacturer be interested in this quantity?13.94PAE13.95PAE13.96PAEAs the voltaic cell shown here runs, the blue solution gradually gets lighter in color and the gray solution gets darker. (a) What species is oxidized and what is reduced? (b) Which electrode is the anode and which is the cathode? (C) Which metal electrode gains mass? (d) In which direction do electrons flow through the external circuit?13.98PAEFor a voltage-sensitive application, you are working on a battery that must have a working voltage of 0.85 V. The half-cells to be used have a standard cell potential of 0.97 V. What must be done to achieve the correct voltage? What information would you need to look up?13.100PAE13.101PAE13.102PAE13.103PAE13.104 (a) What happens when a current is passed through a solution of dilute sulfuric acid to carry out electrolysis? (b) A 5.00-A current is passed through a dilute solution of sulfuric acid for 30.0 min. What mass of oxygen is produced?A current is passed through a solution of copper(II) sulfate long enough to deposit 14.5 g of copper. What volume of oxygen is also produced if the gas is measured at 24 °C and 0.958 atm of pressure?13.106 Hydrazine, N2H4 , has been proposed as the fuel in a fuel cell in which oxygen is the oxidizing agent. The reactions are N2H4(aq)+4OH-(aq)N2(g)+4H2O(l)+4eO2(g)+2H2O(l)+4e4OH-(aq) (a) Which reaction occurs at the anode and which at the cathode? (b) What is the net cell reaction? (C) If the cell is to produce 0.50 A of current for 50.0 h, what mass in grams of hydrazine must be present? (d) What mass in grams of O2 must be available to react with the mass of N2H4 determined in part (c)?13.107PAE1CO2CO3CO4CO5CO6CO7CO8CO9CO10CO14.1PAE14.2PAE14.3PAE14.4PAE(a) How does 14C enter a living plant? (b) Write the chemical equation for this reaction.14.6PAE14.7PAE14.8PAE14.9PAE14.10PAE14.11PAE14.12PAE14.13PAE14.14PAE14.15PAE14.16PAE14.17PAE14.18PAE14.19PAE14.20PAE14.21PAE14.22PAE14.23PAE14.24PAE14.25PAE14.26PAE14.27PAE14.28PAE14.29PAE14.30PAE14.31PAE14.32PAE14.33PAE14.34PAE14.35PAE14.36PAE14.37PAE14.38PAE14.39PAE14.40PAE14.41PAE14.42PAE14.43PAE14.44PAE14.45PAE14.46PAE14.47PAE14.48PAE14.49PAE14.50PAE14.51PAE14.52PAE14.53PAE14.54PAE14.55PAE14.56PAE14.57PAE14.58PAE14.59PAE14.60PAE14.61PAE14.62PAE14.63PAE14.64PAE14.65PAE14.66PAE14.67PAE14.68PAE14.69PAE14.70PAE14.71PAE14.72PAE14.73PAE14.74PAE14.75PAE14.76PAE14.77PAE14.78PAE14.79PAE14.80PAE14.81PAE14.82PAE14.83PAE14.84PAE14.85PAE14.86PAE14.87PAE14.88PAE14.89PAE14.90PAE14.91PAE14.92PAE14.93PAE14.94PAE14.95PAE14.96PAE14.97PAE14.98PAE14.99PAE14.100PAE14.101PAE14.102PAE14.103PAE14.104PAE14.105PAE14.106PAE14.107PAE