Chemistry 223 Spring 2012 Oregon State University Exam 2 May 24, 2012 Drs. Nafshun, Watson, Richardson

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1 Chemistry 223 Spring 2012 Oregon State University Exam 2 May 24, 2012 Drs. Nafshun, Watson, Richardson Instructions: You should have with you several number two pencils, an eraser, your 3" x 5" note card, a calculator, and your University ID Card. If you have notes with you, place them in a sealed backpack and place the backpack OUT OF SIGHT or place the notes directly on the table at the front of the room. Fill in the front page of the Scantron sheet with your last name, first name, middle initial, student identification number, and section number (below). Leave the test form number blank. Section 001 (MWF 8am with Dr. Nafshun) Section 002 (MWF 9am with Dr. Nafshun) Section 003 (MWF 11am with Dr. Watson) Section 004 (MWF 1pm with Dr. Richardson) Section 005 (MWF 3pm with Dr. Nafshun) This exam consists of 22 multiple-choice questions; each has 5 points attached. The last question (Question 23) has 2 points attached. When you finish this exam, proceed to the proctor. Submit your completed Scantron form. You may take your notecard and exam packet with you.

Spectrochemical series: CN - > NO 2 - > en > NH 3 > NCS - > H 2 O > OH - > F - > Cl - F = 96,485 C/mole e - R = 8.314 J/mol K N A = 6.

2 Spectrochemical series: CN - > NO 2 - > en > NH 3 > NCS - > H 2 O > OH - > F - > Cl - F = 96,485 C/mole e - R = J/mol K N A = 6.02 x S = k ln W h = x J s/photon Gº rxn = -RT ln K G rxn = Gº rxn + RT ln Q c = 3.00 x 10 8 m/s E cell = E cell - ln Q Gº = -nf E cell G = H - T S E = hc/ K = ºC

4 Reduction Half-Reaction E º, volt Acidic Solution F 2 (g) + 2 e - 2F - (aq) O 3 (g) + 2 H + (aq) + 2 e - O 2 (g) + H 2 O(l) S 2 O 2-8 (aq) + 2 e - 2 SO 2-4 (aq) H 2 O 2 (aq) + 2H + (aq) + 2 e - 2 H 2 O(l) MnO - 4 (aq) + 8H + (aq) + 5 e - Mn 2+ (aq) + 4 H 2 O(l) PbO 2 (s)+ 4H + (aq) + 2 e - Pb 2+ (aq) + 2 H 2 O(l) Cl 2 (g) + 2 e - 2 Cl - (aq) Cr 2 O 2-7 (aq) + 14 H + (aq) + 6 e - 2 Cr 3+ (aq) + 7 H 2 O(l) MnO 2 (s) + 4H + (aq) + 2 e - Mn 2+ (aq) + 2 H 2 O(l) O 2 (g) + 4H + (aq) + 4 e - 2 H 2 O(l) IO - 3 (aq) +12H + (aq) + 10 e - I 2 (s) + 6 H 2 O(l) Br 2 (l) + 2 e - 2 Br - (aq) NO - 3 (aq) + 4H + (aq) + 3 e - NO(g) + 2 H 2 O(l) Ag + (aq) + e - Ag(s) Fe 3+ (aq) + e - Fe 2+ (aq) O 2 (g) + 2H + (aq) + 2 e - H 2 O 2 (aq) I 2 (s) + 2 e - 2 I - (aq) I - 3 (aq) + 2 e - 3 I - (aq) Cu 2+ (aq) + 2 e - Cu(s) SO 2-4 (aq) + 4H + (aq) + 2 e - 2 H 2 O(l) + SO 2 (g) Sn 4+ (aq) + 2 e - Sn 2+ (aq) S(s) + 2H + (aq) + 2 e - H 2 S(g) H + (aq) + 2 e - H 2 (g) 0 Pb 2+ (aq) + 2 e - Pb(s) Sn 2+ (aq) + 2 e - Sn(s) Co 2+ (aq) + 2 e - Co(s) Cr 3+ (aq) + e - Cr 2+ (aq) Fe 2+ (aq) + 2 e - Fe(s) Zn 2+ (aq) + 2 e - Zn(s) Al 3+ (aq) + 3 e - Al(s) Mg 2+ (aq) + 2 e - Mg(s) Na + (aq) + e - Na (s) Ca 2+ (aq) + 2 e - Ca(s) K + (aq) + e - K(s) Li + (aq) + e - Li(s) Basic Solution O 3 (g) + H 2 O(l) + 2 e - O 2 (g) + 2 OH - (aq) OCl - (g) + H 2 O(l) + 2 e - Cl - (aq) + 2 OH - (aq) O 2 (g) + 2 H 2 O(l) + 4 e - 4 OH - (aq) H 2 O(l) + 2 e - H 2 (g) + 2 OH - (aq)

5 1. The complex: is polar and is cis-[cof 3 (CN) 3 ] 3- is non-polar trans-[cof 3 (CN) 3 ] 3- is polar and is fac-[cof 3 (CN) 3 ] 3- is polar and is mer-[cof 3 (CN) 3 ] 3- is non-polar and is mer-[cof 3 (CN) 3 ] 3-2. How many unpaired electrons are present in the transition metal ion d-orbitals in [FeF 6 ] 4-? A transition metal complex appears orange and absorbs light of 460 nm. What is the energy splitting of the d orbitals ( ) in kj/mol? 4.32 x kj/mol 260 kj/mol 4.32 x kj/mol kj/mol 2.60 x 10-7 kj/mol

6 4. Which of the following is FALSE? The d z 2 and d x 2- y 2 orbitals are higher in energy than the d xy, d xz, and d yz orbitals in octahedral complexes. The electrons on a ligand are directed toward the lobes of the d z 2 or d x 2- y 2 orbitals in octahedral complexes. Ligand electrons overlap with metal ion orbital lobes causing repulsion. The figure below can represent the d x 2- y 2 orbital surrounded by six Lewis Bases in an octahedral coordination metal ion complex. is the energy difference between the d z 2 and d x 2- y 2 orbitals in an octahedral complex.

7 5. It has been suggested that the decomposition of nitroglycerine [suggested overall unbalanced reaction: C 3 H 5 (ONO 2 ) 3 (l) CO 2 (g) + H 2 O (g) + N 2 (g) + O 2 (g)] is spontaneous. Which of the following would NOT support to this conclusion? Many strong bonds in the reactant are replaced with few weak bonds in the products. The process is exothermic. There are more microstates associated with the products than with the reactant. The entropy of the system increases as the process proceeds. S reaction is greater than zero. 6. For which one of the following reactions does the entropy of the system INCREASE? NH 3 (g) + HCl (g) NH 4 Cl (s) Ag + (aq) + Cl - (aq) AgCl (s) 2 H 2 (g) + O 2 (g) 2 H 2 O (g) NH 3 (g) + H 2 O (l) NH + 4 (aq) + OH - (aq) 2 H 2 O 2 (l) 2 H 2 O (l) + O 2 (g)

8 7. Consider the gas-phase hydrogenation of ethylene, C 2 H 2, to produce ethane, C 2 H 6 : C 2 H 2 (g) + 2 H 2 (g) C 2 H 6 (g) Substance H f o, kj mol -1 S o, J mol -1 K -1 C 2 H 2 (g) H 2 (g) C 2 H 6 (g) Under standard conditions, which of the following statements is TRUE? The reaction is spontaneous; H o is favorable while S o is not. The reaction is spontaneous; S o is favorable while H o is not. The reaction is not spontaneous; S o is favorable while H o is not. The reaction is not spontaneous; H o is favorable while S o is not. The reaction is not spontaneous; neither H o nor S o are favorable. 8. One mole of liquid water at room temperature consists of: 1 microstate microstates 69.9 microstates x microstates 1 x 10 2,000,000,000,000,000,000,000,000 microstates

9 9. Which of the following has the greatest entropy associated with it? One mole of Ar (g) at 298 K One mole of C 8 H 18 (l) at 298 K One mole of C 8 H 18 (g) at 298 K One mole of C 8 H 18 (g) at 500 K One mole of Ar (s) at 0 K 10. Consider the following system at K and constant pressure. 4 NH 3 (g) + 3 O 2 (g) 2 N 2 (g) + 6 H 2 O (g); ΔH = kj. Calculate ΔS system and predict whether or not this reaction will be spontaneous at K. ΔS system = kj/k and the process is not spontaneous ΔS system = kj/k and the process is not spontaneous ΔS system = kj/k and the process is spontaneous ΔS system = kj/k and the process is spontaneous ΔS system = kj/k and it is not possible to predict the spontaneity of this process without additional information 11. For the boiling of a certain alcohol, (liquid) (gas); H o = kj/mol and S o = J/mol K. What is the boiling point of the alcohol? 54 ºC 57 ºC 60 ºC 63 ºC 336 ºC

10 12. The K a for acetic acid, CH 3 COOH (aq) is 1.80 x 10-5 at 25 ºC. What is the change in standard free energy at 25 ºC? 4.74 kj/mol 27.1 kj/mol 11.9 kj/mol 4.46 x 10-2 kj/mol 4.46 x 10-7 kj/mol 13. Which statement is true if the following reaction is spontaneous as written? Zn (s) + Cu 2+ (aq) Zn 2+ (aq) + Cu (s) K c is larger than 1, ΔG is negative, and E is positive. K c is larger than 1, ΔG is positive, and E is negative. K c is larger than 1, ΔG is negative, and E is negative. K c is smaller than 1, ΔG is negative, and E is positive. K c is smaller than 1, ΔG is positive, and E is negative.

11 14. Which of the following statements is FALSE? A non-spontaneous process at standard conditions can be spontaneous at a nonstandard temperature. A non-spontaneous process at standard conditions can be spontaneous at nonstandard concentrations. A spontaneous process at standard conditions can be non-spontaneous at a nonstandard temperature. A process is spontaneous if G reaction < 0. A non-spontaneous process will always become spontaneous at a higher temperature. 15. The oxidation number of niobium in K 2 NiF 7 is:

12 16. Consider a cell in which one beaker contains aqueous copper nitrate [Cu(NO 3 ) 2 ] and a copper metal electrode and the other beaker contains aqueous zinc nitrate [Zn(NO 3 ) 2 ] and a zinc metal electrode. Which of the following statements is false? The theoretical cell voltage is V A salt bridge is used to allow the flow of ions but restrict the flow of electrons The mass of the zinc electrode will decrease as the process proceeds The concentration of Cu 2+ (aq) increases as the process proceeds Electrons flow from the zinc compartment to the copper compartment 17. Consider fuel cell technology and the hydrogen economy. Which of the following is FALSE? A hydrogen fuel cell produces a potential (a voltage). Because the potential for a single hydrogen fuel cell is near 1 volt, many fuel cells may be combined in a fuel cell stack to produce greater voltages. The hydrogen fuel cell demonstrated in class input hydrogen and oxygen gases. Fuel cells produce energy for free because of the widespread availability of H 2. The hydrogen fuel cell demonstrated in class contains a platinum catalyst to facilitate the process. This platinum catalyst produced oxygen atoms from oxygen molecules. The oxygen atoms are then combined with electrons and protons to produce water. 18. The calculated cell potential for a 2 Al (s) + 3 Pb 2+ (aq) 2 Al 3+ (aq) + 3 Pb (s) cell is: V V V V V

13 19. A student provides a current of amps through a solution of Cr 3+ (aq). The voltage is such that chromium metal is deposited at the cathode. How long must the current be applied to plate 42.0 grams of Cr (s)? 3.50 hours 10.5 hours 1.80 hours 779 hours 5.41 hours 20. Consider Li (s), Cr 3+ (aq), Cr (s), Br 2 (l), and Li + (aq). The strongest oxidizing agent is: Li (s) Cr 3+ (aq) Cr (s) Br 2 (l) Li + (aq) 21. When the reaction Cr (s) + B 2 O 5 2- (aq) B 2+ (aq) + Cr 3+ (aq) is correctly balanced in acid, 3 protons (H + ) are consumed 10 protons (H + ) are consumed 20 protons (H + ) are consumed 30 protons (H + ) are consumed 42 protons (H + ) are consumed

14 22. The expression E cell = E cell - ln Q is referred to as the Nernst Equation. Which of the following is FALSE? Given the standard cell potential, the Nernst Equation can be used to calculate the potential of a cell at temperatures other than 298 K. The cell potential for the process in which: 2 Al (s) + 3 Zn 2+ (aq; 1.00 M) 2 Al 3+ (aq; M) + 3 Zn (s) will be greater than the cell potential for the process in which: 2 Al (s) + 3 Zn 2+ (aq; 1.00 M) 2 Al 3+ (aq; 1.00 M) + 3 Zn (s). n = 6 for the process 2 Al (s) + 3 Zn 2+ (aq) 2 Al 3+ (aq) + 3 Zn (s). Q is the reaction quotient. F = for the process 2 Al (s) + 3 Zn 2+ (aq) 2 Al 3+ (aq) + 3 Zn (s). 23. The CH 223 Final Exam is scheduled for Monday, June 11, 2012, 4:00-5:50pm. Which one of the following statements is FALSE? The CH 123 Final Exam is scheduled for Monday, June 11, 2012, 4:00-5:50pm. The CH 123 Final Exam is scheduled for Monday, June 11, 2012, 4:00-5:50pm. The CH 123 Final Exam is scheduled for Monday, June 11, 2012, 4:00-5:50pm. The CH 123 Final Exam is scheduled for Monday, June 11, 2012, 4:00-5:50pm. Your electrochemistry notes cannot impress your mother enough to entice her into writing a check to you for at least $2500. [Any response will receive full credit; even no response.]

CH 223 SPRING FINAL EXAM June 6, 2011 DO NOT OPEN THIS EXAM UNTIL TOLD TO DO SO

CH 223 SPRING FINAL EXAM June 6, 2011 DO NOT OPEN THIS EXAM UNTIL TOLD TO DO SO CH 223 SPRING 2011 - FINAL EXAM June 6, 2011 This exam has 33 questions worth 5 pts each, plus one question worth 3 pts. The total possible score is 168 pts. DO NOT OPEN THIS EXAM UNTIL TOLD TO DO SO Before