solut11 - CHAPTER ELEVEN ELECTROCHEMISTRY Galvanic Cells...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
313 CHAPTER ELEVEN ELECTROCHEMISTRY Galvanic Cells, Cell Potentials, and Standard Reduction Potentials 15. In a galvanic cell, a spontaneous reaction occurs, producing an electric current. In an electrolytic cell, electricity is used to force a reaction to occur that is not spontaneous. 16. The salt bridge completes the electrical circuit and allows counter ions to flow into the two cell compartments to maintain electrical neutrality. It also separates the cathode and anode compart- ments such that electrical energy can be extracted. If the cathode and anode compartments are not separated the cell would rapidly go to equilibrium without any useful work being done. 17. A typical galvanic cell diagram is: The diagram for all cells will look like this. The contents of each half-cell will be identified for each reaction, with all concentrations at 1.0 M and partial pressures at 1.0 atm. Note that cations always flow into the cathode compartment and anions always flow into the anode compartment. This is required to keep each compartment electrically neutral. a. Reference Table 11.1 for standard reduction potentials. Remember that ° E cell = E ° (cathode) - E ° (anode); in the Solutions Guide, we will represent E ° (cathode) as ° E c and represent -E ° (anode) as ° E - a . Also remember that standard potentials are not multiplied by the integer used to obtain the overall balanced equation. (Cl 2 + 2 e - 2 Cl - ) × 3 ° E c = 1.36 V 7 H 2 O + 2 Cr 3+ Cr 2 O 7 2- + 14 H + + 6 e - ° E - a = -1.33 V
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
314 7 H 2 O(l) + 2 Cr 3+ (aq) + 3 Cl 2 (g) Cr 2 O 7 2- (aq) + 6 Cl - (aq) + 14 H + (aq) ° E cell = 0.03 V The contents of each compartment is: Cathode: Pt electrode; Cl 2 bubbled into solution, Cl - in solution Anode: Pt electrode; Cr 3+ , H + , and Cr 2 O 7 2- in solution We need a nonreactive metal to use as the electrode in each case, since all of the reactants and products are in solution. Pt is the most common choice. Another possibility is graphite. b. Cu 2+ + 2 e - Cu ° E c = 0.34 V Mg Mg 2+ + 2 e - - ° E a = 2.37 V Cu 2+ (aq) + Mg(s) Cu(s) + Mg 2+ (aq) ° E cell = 2.71 V Cathode: Cu electrode; Cu 2+ in solution Anode: Mg electrode; Mg 2+ in solution c. 5 e - + 6 H + + IO 3 - 1/2 I 2 + 3 H 2 O ° E c = 1.20 V (Fe 2+ Fe 3+ + e - ) × 5- ° E a = -0.77 V 6 H + + IO 3 - + 5 Fe 2+ 5 Fe 3+ + 1/2 I 2 + 3 H 2 ° E cell = 0.43 V or 12 H + (aq) + 2 IO 3 - (aq) + 10 Fe 2+ (aq) 10 Fe 3+ (aq) + I 2 (s) + 6 H 2 O(l) ° E cell = 0.43 V Cathode: Pt electrode; IO 3 - , I 2 and H 2 SO 4 (H + source) in solution. Anode: Pt electrode; Fe 2+ and Fe 3+ in solution Note: I 2 (s) would make a poor electrode since it sublimes. d. (Ag + + e - Ag) × 2 ° E c = 0.80 V Zn Zn 2+ + 2 e - - ° E a = 0.76 V Zn(s) + 2 Ag + (aq) 2 Ag(s) + Zn 2+ (aq) ° E cell = 1.56 V Cathode: Ag electrode; Ag + in solution Anode: Zn electrode; Zn 2+ in solution 18. a. 2 Ag + + 2 e - 2 Ag ° E c = 0.80 V
Background image of page 2
CHAPTER 11 ELECTROCHEMISTRY 315 Cu Cu 2+ + 2 e - - ° E a = -0.34 V 2 Ag + (aq) + Cu(s) Cu 2+ (aq) + 2 Ag(s) ° E cell = 0.46 V Spontaneous at standard conditions ( ° E cell > 0).
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CHAPTER 11 ELECTROCHEMISTRY 316 b. Zn 2+ + 2 e - Zn ° E c = -0.76 V Ni Ni 2+ + 2 e - - ° E a = 0.23 V Zn 2+ (aq) + Ni(s) Zn(s) + Ni 2+ (aq) ° E cell = -0.53 V Not spontaneous at standard conditions ( ° E cell < 0).
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

This homework help was uploaded on 04/06/2008 for the course CHEM 142 taught by Professor Zoller,williamh during the Fall '07 term at University of Washington.

Page1 / 39

solut11 - CHAPTER ELEVEN ELECTROCHEMISTRY Galvanic Cells...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online