Circle the letters only. NO ANSWERS in the Columns!

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1 Chemistry Name (please print) Exam 5 (100 points) April 18, 2018 On my honor, I have neither given nor received unauthorized aid on this exam. Signed Date Circle the letters only. NO ANSWERS in the Columns! 1. (3 points) A galvanic cell has the overall reaction: 2 Fe(NO 3 ) 2 (aq) + Pb(NO 3 ) 3 (aq) 2 Fe(NO 3 ) 3 (aq) + Pb (s) Which is the half reaction occurring at the anode? a. Fe 3+ (aq) + e - Fe 2+ (aq) d. NO - 3 (aq) + 2 H + (aq) + e - NO 2 (g) + H2O (l) b. Pb 2+ (aq) + 2 e - Pb (s) e. NO - 3 (aq) + 4 H + (aq) + 3 e - NO (g) + 2 H2O (l) c. Fe 2+ (aq) Fe 3+ (aq) + e - f. Pb (s) Pb 2+ (aq) + 2 e - 2. (3 points) For the reaction, 2 Cr 2+ (aq) + Cl 2 (g) 2 Cr 3+ (aq) + 2 Cl - (aq), E cell is 1.78 V. Calculate E cell for the related reaction Cr 3+ (aq) + Cl - (aq) Cr 2+ (aq) + 1 /2 Cl 2 (g). a V d V b V e V c V f. None of these. 3. (6 points) How many grams of chromium would be electroplated by passing a constant current of 5.2 amperes through a solution containing CrCl 3 for 45.0 min? a g d. 24 g b g e. 2.5 g c g f. 2.4 x 10 5 g 4. (6 points) Calculate G for the electrochemical cell Fe (s) Fe 2+ (aq) Sn 4+ (aq), Sn 2+ (aq) Pt(s) a. 1.2 x 10 2 kj/mol b. 1.1 x 10 2 kj/mol c. 1.1 x 10 5 J/mol d. 5.5 x 10 1 kj/mol e. 6.0 x 10 1 kj/mol f. none of these 5. Circle the terms that correctly complete the following sentences. a. (4 points) The value of S for the reaction below is expected to be (a) positive, (b) negative, or (c) zero. b. (4 points) The reaction is expected to be spontaneous at (a) all temperatures, (b) low temperatures, or (c) high temperatures. 2 CO 2 (g) 2 CO (g) + O 2 (g) H = 566 kj

2 page 2 6. (10 points) Balance the following redox reaction which occurs in basic solution. I 2 + ClO 3 IO3 + Cl BALANCED (BASIC) Reduction Half Reaction: BALANCED (BASIC) Oxidation Half Reaction: Net Ionic Equation: 7. (14 points) Using the thermodynamic data provided below, calculate K sp for ZnS (s) at 25 C. SHOW ALL WORK and appropriate CHEMICAL REACTIONS. H f (kj/mol) S (J/K mol) Zn 2+ (aq) S 2- (aq) ZnS (s)

3 page 3 8. A piece of nickel metal weighing grams is placed in ml of M AgNO 3 at 25 C. After the mixture comes to equilibrium, determine the following: a. (8 points) the amount of nickel metal that remains? SHOW ALL WORK and appropriate CHEMICAL REACTIONS. b. (14 points) the concentrations of Ni 2+ and Ag + in the solution, assuming there is no change in volume? SHOW ALL WORK LOGICALLY.

4 page 4 9. Consider the following galvanic cell in which the volume of each half-cell is 500 ml. Pb (s) PbO (s) OH - (1.00 M) Ag + (1.00 M) Ag (s) a. (9 points) Write balanced chemical equations for the two half-reactions and for the overall cell reaction. Anode: Cathode: Cell: b. (5 points) Determine the standard potential (E cell ) for this cell. c. (14 points) SHOW ALL WORK. What is the cell potential after a current is drawn from the cell at a constant rate of amp for 72 hours?

5 Some Standard Reduction Potentials E (volts) Cl 2 (g) + 2 e - 2 Cl - (aq) 1.36 O 2 (g) + 4 H + (aq) + 4 e - 2 H 2 O 1.23 Ag + (aq) + 1 e - Ag(s) 0.80 Fe 3+ (aq) + e - Fe 2+ (aq) 0.77 O 2 (g) + 2 H + (aq) + 2 e - H 2 O 2 (aq) 0.68 Cu 2+ (aq) + 2 e - Cu(s) 0.34 Sn 2+ (aq) + 2 e - Sn 4+ (aq) H + (aq) + 2 e - H 2 (g) 0 Fe 2+ (aq) + 2 e - Fe(s) PbO(s) + H 2 O(l) + 2 e - Pb(s) + 2 OH - (aq) Cr +3 (aq) + 3 e - Cr(s) Zn +2 (aq) + 2 e - Zn(s) H 2 O (l) + 2 e - 2 OH - (aq) + H 2 (g) Al 3+ (aq) + 3 e - Al(s) U 3+ (aq) + 3 e - U(s) Mg +2 (aq) + 2 e - Mg(s) Periodic Table of the Elements Faraday's constant 96,500 coul/mole e - IA VIIIA (1) (18) 1 2 gas constant (R) L. atm/mol. K (2) J/mole. K (13) (14) (15) (16) (17) speed of light (c) 3.00 x 10 8 m/s specific heat of water (s) J/g. C Planck's constant 6.63 x J. s H IIA IIIA IVA VA VIA VIIA He 2 Li Be B C N O F Ne Na Mg IIIB IVB VB VIB VIIB VIIIB IB IIB Al Si P S Cl Ar (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Unq Unp Unh Uns Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

6 Chemistry Name (please print) Exam 5 (100 points) April 18, 2018 On my honor, I have neither given nor received unauthorized aid on this exam. Signed Date Circle the letters only. NO ANSWERS in the Columns! 1. (3 points) A galvanic cell has the overall reaction: 2 Fe(NO 3 ) 2 (aq) + Pb(NO 3 ) 3 (aq) 2 Fe(NO 3 ) 3 (aq) + Pb (s) Which is the half reaction occurring at the anode? a. Fe 3+ (aq) + e - Fe 2+ (aq) d. NO - 3 (aq) + 2 H + (aq) + e - NO 2 (g) + H2O (l) b. Pb 2+ (aq) + 2 e - Pb (s) e. NO - 3 (aq) + 4 H + (aq) + 3 e - NO (g) + 2 H2O (l) c. Fe 2+ (aq) Fe 3+ (aq) + e - f. Pb (s) Pb 2+ (aq) + 2 e - 2. (3 points) For the reaction, 2 Cr 2+ (aq) + Cl 2 (g) 2 Cr 3+ (aq) + 2 Cl - (aq), E cell is 1.78 V. Calculate E cell for the related reaction Cr 3+ (aq) + Cl - (aq) Cr 2+ (aq) + 1 /2 Cl 2 (g). a V d V b V e V c V f. None of these. 3. (6 points) How many grams of chromium would be electroplated by passing a constant current of 5.2 amperes through a solution containing CrCl 3 for 45.0 min? a g d. 24 g b g e. 2.5 g c g f. 2.4 x 10 5 g 4. (6 points) Calculate G for the electrochemical cell Fe (s) Fe 2+ (aq) Sn 4+ (aq), Sn 2+ (aq) Pt(s) a. 1.2 x 10 2 kj/mol b. 1.1 x 10 2 kj/mol c. 1.1 x 10 5 J/mol d. 5.5 x 10 1 kj/mol e. 6.0 x 10 1 kj/mol f. none of these 5. Circle the terms that correctly complete the following sentences. a. (4 points) The value of S for the reaction below is expected to be (a) positive, (b) negative, or (c) zero. b. (4 points) The reaction is expected to be spontaneous at (a) all temperatures, (b) low temperatures, or (c) high temperatures. 2 CO 2 (g) 2 CO (g) + O 2 (g) H = 566 kj

7 page 2 6. (10 points) Balance the following redox reaction which occurs in basic solution. Reduction Half Reaction: CrO S2 O 8 2- CrO SO4 2- Oxidation Half Reaction: Net Ionic Equation: 7. (14 points) Using the thermodynamic data provided below, calculate K sp for ZnS (s) at 25 C. SHOW ALL WORK and appropriate CHEMICAL REACTIONS. H f (kj/mol) S (J/K mol) Zn 2+ (aq) S 2- (aq) ZnS (s)

8 page 3 8. A piece of nickel metal weighing grams is placed in ml of M AgNO 3 at 25 C. After the mixture comes to equilibrium, determine the following: a. (8 points) the amount of nickel metal that remains? SHOW ALL WORK and appropriate CHEMICAL REACTIONS. b. (14 points) the concentrations of Ni 2+ and Ag + in the solution, assuming there is no change in volume? SHOW ALL WORK LOGICALLY.

9 page 4 9. Consider the following galvanic cell in which the volume of each half-cell is 500 ml. Pb (s) PbO (s) OH - (1.00 M) Ag + (1.00 M) Ag (s) a. (9 points) Write balanced chemical equations for the two half-reactions and for the overall cell reaction. Anode: Cathode: Cell: b. (5 points) Determine the standard potential (E cell ) for this cell. c. (14 points) SHOW ALL WORK. What is the cell potential after a current is drawn from the cell at a constant rate of amp for 72 hours?