Circle the letters only. NO ANSWERS in the Columns!

Chemistry 1304.001 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. 1.78 V d. 3.56 V b. 0.89 V e. 0.89 V c. 1.78 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. 2.3 10 10 g d. 24 g b. 9.3 10-4 g e. 2.5 g c. 0.042 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

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) 152.4 106.5 S 2- (aq) 41.8 22 ZnS (s) 203 57.7

page 3 8. A piece of nickel metal weighing 1.882 grams is placed in 100.0 ml of 0.200 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.

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 0.175 amp for 72 hours?

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) 0.15 2 H + (aq) + 2 e - H 2 (g) 0 Fe 2+ (aq) + 2 e - Fe(s) - 0.44 PbO(s) + H 2 O(l) + 2 e - Pb(s) + 2 OH - (aq) -0.58 Cr +3 (aq) + 3 e - Cr(s) -0.74 Zn +2 (aq) + 2 e - Zn(s) -0.76 2 H 2 O (l) + 2 e - 2 OH - (aq) + H 2 (g) -0.83 Al 3+ (aq) + 3 e - Al(s) - 1.67 U 3+ (aq) + 3 e - U(s) - 1.80 Mg +2 (aq) + 2 e - Mg(s) -2.37 Periodic Table of the Elements Faraday's constant 96,500 coul/mole e - IA VIIIA (1) (18) 1 2 gas constant (R) 0.082057 L. atm/mol. K 1.0080 (2) 8.314 J/mole. K (13) (14) (15) (16) (17) 4.0026 3 4 speed of light (c) 3.00 x 10 8 m/s 5 6 7 8 9 10 specific heat of water (s) 4.184 J/g. C 6.9410 9.0122 Planck's constant 6.63 x 10-34 J. s 10.811 12.011 14.007 15.999 18.998 20.179 1 H IIA IIIA IVA VA VIA VIIA He 2 Li Be B C N O F Ne 11 12 13 14 15 16 17 18 3 Na Mg IIIB IVB VB VIB VIIB........ VIIIB........ IB IIB Al Si P S Cl Ar 22.990 24.305 (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) 26.982 28.086 30.974 32.066 35.453 39.948 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 39.098 40.078 44.956 47.880 50.942 51.996 54.938 55.847 58.933 58.690 63.546 65.380 69.723 72.610 74.922 78.960 79.904 83.800 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 85.468 87.620 88.906 91.224 92.906 95.940 98.907 101.07 102.91 106.42 107.87 112.41 114.82 118.71 121.75 127.60 126.90 131.29 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 132.91 137.33 138.91 178.49 180.95 183.85 186.21 190.20 192.22 195.09 196.97 200.59 204.38 207.20 208.98 208.98 209.99 222.02 87 88 89 104 105 106 107 7 Fr Ra Ac Unq Unp Unh Uns 223.02 226.03 227.03 261.11 262.11 263.12 262.12 58 59 60 61 62 63 64 65 66 67 68 69 70 71 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 140.12 140.91 144.24 145.91 150.36 151.97 157.25 158.93 162.50 164.93 167.26 168.93 173.04 174.97 90 91 92 93 94 95 96 97 98 99 100 101 102 103 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 232.04 231.04 238.03 237.05 244.06 243.06 247.07 247.07 242.06 252.08 257.10 258.10 259.10 260.11

page 2 6. (10 points) Balance the following redox reaction which occurs in basic solution. Reduction Half Reaction: CrO 2 - + S2 O 8 2- CrO4 2- + 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) 152.4 106.5 S 2- (aq) 41.8 22 ZnS (s) 203 57.7