14-19. (a) Write the half-reactions for a H2 -O2 fuel cell. Find the theoretical cell voltage at 25°C if P H₂ 1.0 = ar,P b 2ar, and [H] = 0.5M at both electrodes. (Real fuel cells operate at temperatures of = 02 0.2 b 60° 1000°C and produce 0.7V.) (b) If the cell is 70% efficient at converting chemical energy into electrical energy, and a stack of cells produces 20 kW at 220 V, how many grams of H2 are consumed in an hour? (c) In the U.S., engines are frequently rated in "horsepower." Use Table 1-4 to convert 20 kW to horsepower.

14-19. (a) Write the half-reactions for a H2 -O2 fuel cell. Find the theoretical cell voltage at 25°C if P H₂ 1.0 = ar,P b 2ar, and [H] = 0.5M at both electrodes. (Real fuel cells operate at temperatures of = 02 0.2 b 60° 1000°C and produce 0.7V.) (b) If the cell is 70% efficient at converting chemical energy into electrical energy, and a stack of cells produces 20 kW at 220 V, how many grams of H2 are consumed in an hour? (c) In the U.S., engines are frequently rated in "horsepower." Use Table 1-4 to convert 20 kW to horsepower.

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter24: Coulometry

Section: Chapter Questions

Problem 24.4QAP: Halide ions can he deposited at a silver anode, the reaction being Ag(s) + X- AgX(s) +e- Suppose...

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Halide ions can he deposited at a silver anode, the reaction being Ag(s) + X- AgX(s) +e- Suppose that a cell was formed by immersing a silver anode in an analyte solution that was 0.0250 M Cl-,Br-, and I -ions and connecting the half-cell to a saturated calomel cathode via a salt bridge. (a) Which halide would form first and at what potential? Is the cell galvanic or electrolytic? (b) Could I- and Br- be separated quantitatively? (Take 1.00 l0-5 M as the criterion for quantitative removal of an ion.) If a separation is feasible, what range of cell potential could he used? (c) Repeat part (b) for I- and Cl-. (d) Repeat part (b) for Br- and Cl-.
The table below lists the cell potentials for the 10 possible galvanic cells assembled from the metals A. B. C. D. and E. and their respective 1.00 M 2+ ions in solution. Using the data in the table, establish a standard reduction potential table similar to Table 17-1 in the text. Assign a reduction potential of 0.00 V to the half-reaction that falls in the middle of the series. You should get two different tables. Explain why, and discuss what you could do to determine which table is correct. A(s)in A2+(aq) B(s)in B2+(aq) C(s)in V2+(aq) D(s)in D2+(aq) E(s)in E2+(aq) 0.28V 0.81V 0.13V 1.00V D(s)in D2+(aq) 0.72V 0.19V 1.13V C(s)in V2+(aq) 0.41V 0.94V B(s)in B2+(aq) 0.53V
Calculate the standard cell potential of the following cell at 25C. Cr(s)Cr3(aq)Hg22(aq)Hg(l)
Galvanic cells harness spontaneous oxidationreduction reactions to produce work by producing a current. They do so by controlling the flow of electrons from the species oxidized to the species reduced. How is a galvanic cell designed? What is in the cathode compartment? The anode compartment? What purpose do electrodes serve? Which way do electrons always flow in the wire connecting the two electrodes in a galvanic cell? Why is it necessary to use a salt bridge or a porous disk in a galvanic cell? Which way do cations flow in the salt bridge? Which way do the anions flow? What is a cell potential and what is a volt?
What is the cell potential of the following cell at 25C? Ni(s)Ni2+(1.0M)Sn2(1.5104M)Sn(s)
Calculate the cell potential of a cell operating with the following reaction at 25C, in which [Cr2O32] = 0.020 M, [I] = 0.015 M, [Cr3+] = 0.40 M, and [H+] = 0.60 M. Cr2O72(aq)+6I(aq)+14H+(aq)2Cr3+(aq)+3I2(s)+7H2O(l)
Calculate the cell potential of a cell operating with the following reaction at 25C, in which [MnO4] = 0.010 M, [Br] = 0.010 M. [Mn2] = 0.15 M, and [H] = 1.0 M. 2MNO4(aq)+10Br(aq)+16H+(aq)2MN2(aq)+5Br2(l)+8H2O(l)
The cell potential of the following cell at 25C is 0.480 V. ZnZn2+(1M)H+(testsolution)H2(1atm)Pt What is the pH of the test solution?
Consider the following galvanic cell: A 15 0-mole sample of NH is added to the Ag compartment (assume 1.00 L of total solution after the addition). The silver ion reacts with ammonia to form complex ions as shown: Ag+(aq)+NH3(aq)AgNH3+(aq)K1=2.1103AgNH3+(aq)+NH3(aq)Ag(NH3)2+(aq)K2=8.2103 Calculate the cell potential after the addition of 15.0 moles of NH3.
Calculate the standard cell potential of the cell corresponding to the oxidation of oxalic acid, H2C2O4, by permanganate ion. MnO4. 5H2C2O4(aq)+2MnO4(aq)+6H+(aq)10CO2(g)+2Mn2+(aq)+8H2O(l) See Appendix C for free energies of formation: Gf for H2C2O4(aq) is 698 kJ.
Table 17-1 lists common half-reactions along with the standard reduction potential associated with each half-reaction. These standard reduction potentials are all relative to some standard. What is the standard (zero point)? lf is positive for a half-reaction, what does it mean? If is negative for a half-reaction, what does it mean? Which species in Table 17-1 is most easily reduced? Least easily reduced? The reverse of the half-reactions in Table 17-1 are the oxidation half-reactions. How are standard oxidation potentials determined? In Table 17-1, which species is the best reducing agent? The worst reducing agent? To determine the standard cell potential for a redox reaction, the standard reduction potential is added to the standard oxidation potential. What must be true about this sum if the cell is to be spontaneous (produce a galvanic cell)? Standard reduction and oxidation potentials are intensive. What does this mean? Summarize how line notation is used to describe galvanic cells.
An electrochemical cell consists of a silver metal electrode immersed in a solution with [Ag+] = 1.0 M separated by a porous disk from a copper metal electrode. If the copper electrode is placed in a solution of 5.0 M NH3 that is also 0.010 M in Cu(NH3)42+, what is the cell potential at 25C? Cu2+(aq)+4NH3(aq)Cu(NH3)42+(aq)K=1.01013