GENERAL CHEMISTRY II CHEM 1412 SYSTEM FINAL EXAM VERSION A Summer 2107 Page1 1
Part I: Multiple Choice (2 points each) 1. The density of 96.0 % H2SO4(aq) is 1.87 g/ml. Calculate the molarity of the solution. A. 18.3 M B. 19.1 M C. 5.23 M D. 5.45 M E. 10.2 M 2. Which of the following will have the highest boiling point? A. Pure H2O B. 0.10 M KNO3(aq) C. 0.10 M AlCl3(aq) D. 0.10 M Na2SO4(aq) E. 0.10 M C6H12O6(aq) 3. What is the freezing point of 0.20 m Ba(NO3)a (aq)? The freezing point depression constant for H2O is 1.86 C/m A. -0.372 C B. -0.744 C C. -1.12 C D. -1.49 C E. -2.24 C 4. The vapor pressure of benzene, C6H6, at 61 C is 400 torr. What is the vapor pressure of the solution prepared by dissolving 0.500 mol of biphenyl, C12H10 in 4.50 mol C6H6? A. 44.4 torr B. 60 torr C. 40.0 torr D. 2000 torr E. 360 torr 5. The half life of a first order reaction A Products is 2.00 min when the initial concentration of A is 1.00 M. What will be the half life of this reaction when the initial concentration of A is 0.500 M? A. 0.347 min B. 1.00 min C. 4.00 min D. 0.250 min E. 2.00 min Page2 2
6. Consider the reaction 2A + 3B 4C + 5D. If the rate of formation of C is 5.00 M/s, what will be the rate of formation of D? A. 4.00 M/s B. 6.25 M/s C. 25.0 M/s D. 20.0 M/s E. 1.25 M/s 7. The rate law for a reaction A + B products is rate = k [A] 2. What will be the effect on the reaction rate if the concentration of B is doubled but the concentration of A is unchanged? A. rate doubles B. rate halved C. rate is unchanged D. rate quadruples E. rate triples 8. The chemical reaction 5Br - (aq) + BrO3 - (aq) + 6H + (aq) 3Br2(aq) + 3H2O(l) has the rate law: rate = k[br - ][BrO3 - ][H + ] 2. What is the overall order of the reaction? A. 5 B. 4 C. 3 D. 2 E. 1 9. For which of the following reactions are the numerical values for Kp and K the same? i. 2SO2(g) + O2(g) 2SO3(g) ii. N2(g) + O2(g) 2NO(g) iii. H2(g) + I2(g) 2HI(g) A. i only B. ii only C. i and ii D. ii and iii E. i, ii. and iii Page3 3
10. Which of the following equilibria will be affected by changes in container volume? i. 2SO2(g) + O2(g) 2SO3(g) ii. N2(g) + O2(g) 2NO(g) iii. H2(g) + I2(g) 2HI(g) A. i only B. ii only C. i and ii D. ii and iii E. i, ii, & iii 11. Consider the equilibrium: 2NH3 (g) N2 (g) + 3H2 (g) H = 46.1 kj at 298K Which one of the following disturbances will cause the equilibrium to shift to the right? A. Increasing the temperature. B. Adding a catalyst. C. Increasing the partial pressure of N2. D. Removing NH3. E. Decreasing the container volume. 12. At 184 o C, the equilibrium constant K is 1.48 X 10 4 for the reaction: 2 NO (g) + O2 (g) 2 NO2 (g) Calculate the value of K for the following reaction: A. 5.92 10 4 B. 6.76 10 5 C. 4.56 10 9 D. 2.19 10 8 E. 1.35 10 4 4NO2 (g) 4NO (g) + 2O2 (g) 13. Which of the following pairs of species is not a conjugate acid-base pair? A. H2S, S -2 B. HNO2, NO2 - C. OH -, O 2- D. HSO4 -, SO4 2- E. H 2CO 3, HCO 3 - Page4 4
14. Which of the following reactions is associated with the definition of Kb? A. HCN - (aq) + F - (aq) CN - (aq) + HF(aq) B. F - (aq) + H2O(l) HF(aq) + OH - (aq) C. Zn(OH2)6 2+ (aq) [Zn(OH2)5OH] + (aq) + H + (aq) D. HCN(aq) + H2O(l) CN - (aq) + H3O + E. none of the above 15. What is the ph of 0.023 M HCN (aq)? (Ka = 4.9 x 10 10 ) A. 1.64 B. 10.95 C. 3.05 D. 5.47 E. 4.97 16. What is the ph of 0.020 M Ba(OH)2(aq)? A. 1.70 B. 12.30 C. 1.40 D. 12.60 E. 12.00 17. Pick the weakest of the following oxyacids: A. HClO4 B. H2SO4 C. H2SeO4 D. H2SeO3 E. H2SO3 18. The aqueous solutions of which of the following salts will have a ph < 7? A. KNO3 B. KNO2 C. NH4NO3 D. All of the above E. None of the above Page5 5
19. Which one of the following combinations cannot function as a buffer solution? A. HCN and KCN B. HF and NaF C. NH3 and (NH4)2SO4 D. HNO2 and NaNO2 E. HNO3 and NaNO3 20. Calculate the ph of buffer solution is prepared by taking 0.250 moles of acetic acid ( pka = 4.74) and 0.400 moles of sodium acetate in sufficient water to make 1.800 liters of solution. A. 4.94 B. 4.66 C. 4.86 D. 4.56 E. 4.74 21. What is the Ksp expression for magnesium phosphate, Mg3(PO4)2? A. Ksp = [Mg 2+ ] 2 [PO4 3- ] 3 B. Ksp= [Mg 2+ ] 3 [PO4 3- ] 2 C. Ksp= [Mg 2+ ] 3 [PO4 3- ] D. Ksp= [Mg 2+ ] [PO4 3- ] E. Ksp= [Mg 2+ ] [PO4 3- ] 2 22. The solubility of silver oxalate, Ag2C2O4, in pure water is 2.06 x 10-4 moles per liter. Calculate the value of Ksp for silver oxalate from this data. A. 4.24 x 10-8 B. 8.49 x 10-8 C. 1.75 x 10-11 D. 3.50 x 10-11 E. 8.24 x 10-12 23. For a reaction, if G o = 0, then A. S o = 0 B. K = 0 C. H o = 0 D. K = 1 E. G = 0 Page6 6
24. What is the value of ΔG at 298K for the reaction, Pb(s) + 2 H + (aq) Pb 2+ (aq) + H 2 (g)? E = 0.13 V. A. 12 kj B. -25000 kj C. 25 kj D. -25 kj E. 39 kj 25. For which of the following processes would S o be expected to be most positive? A. H2O(l) H2O(s) B. NH3(g) + HCl(g) NH4Cl(s) C. O2(g) + 2H2(g) 2H2O(g) D. N2O4(g) 2NO2(g) E. 2NH4NO3(s) 2N2(g) + O2(g) + 4H2O(g) 26. Using the standard entropy values: H2(g), S o = + 130.6 J mol -1 K -1 I2(s), S o = + 116.12 J mol -1 K -1 HI(g), S o = + 206.5 J mol -1 K -1 Calculate the standard entropy change, S o, for the reaction: H2(g) + I2(g) 2 HI(g) A. -40.8 J B. +40.8 J C. -166.3 J D. +166.3 J E. 121 J 27. For the reaction: A(g) + 2B(g) 4C(g), G = 77.8 kj. If the reaction mixture consists of 2.0 atm, 4.0 atm B, and 2.5 atm C at 298 K, calculate the G for this reaction mixture at 298 K. (R=8.314 J/molK). A. 78.3 kj B. 7.89 kj C. 7.89 kj D. -34.2 kj E. 34.2 kj Page7 7
28. The standard reduction potentials for the following half reactions are given as follows; Cr+3 +3e- Cr(s) E0 = - 0.73 V Br2(aq) + 2e- 2Br- E0 = + 1.09 V What is the E for this cell? A. 1.82 V B. 0.36 V C. 4.75 V D. 1.79 V E. 0.72 V 29. In the cell shown, which reaction occurs at the cathode? Cu(s) Cu2+(aq) Ag+(aq) Ag(s) A. Cu2+(aq) + 2 e- Cu(s) B. Ag(s) Ag+(aq) + e- C. Ag+(aq) + e- Ag(s) D. Cu(s) Cu2+(aq) + 2 e 30. Consider the following standard reduction potentials in acid solution: Cr 3+ + 3e Cr E = 0.74 V Co 2+ + 2e Co E = 0.28 V MnO4 + 8H + + 5e Mn 2+ + 4H2O E = +1.51 V The strongest oxidizing agent listed above is A. Cr 3+. B. Cr. C. Mn 2+. D. Co 2+. E. MnO4. 31. What mass in grams of copper will be deposited from a solution of Cu2+ by a current of 2.50 A in 2.00 hr? A. 11.90 B. 5.93 C. 23.7 D. 1.65 E. 5.00 Page8 8
32. A radioisotope decays to give an alpha particle and Pb-208. What was the parent isotope? A. Bi-208 B. Tl-208 C. Po-212 D. Hg-210 E. Po-210 33. C-14 undergoes beta decay to form what nucleus? A. B-13 B. B-15 C. N-14 D. N-15 E. B-14 34. What is the IUPAC name for the following compound? A. 4,6,8-trimethylnonane B. 2,4 -dimethylnonane C. 2,4,6-trimethylnonane D. 4,6,8-methylnonane E. none of these 35. Classify the following molecule: O A. ester B. ether C. aldehyde D. ketone E. carboxylic acid CH 3 - CH 2 - CH 2 - C O -CH 3 Page9 9
PARTIAL CREDIT PROBLEMS-SHOW ALL YOUR WORK TO GET FULL CREDIT-5 pts each. 1. A 0.980 g sample of an unknown molecular compound is dissolved in an appropriate solvent at 25 C. The volume of the resulting solution is 200.0 ml and an osmotic pressure of 5.20 torr. What is the molar mass of the unknown compound? 2. The following rate data was collected for a reaction X + Y Products Exp. [X] [Y] Rate of formation of a product 1 0.23 M 0.17 M 0.33 M/h 2 0.46 M 0.17 M 0.66 M/h 3 0.23 M 0.51 M 0.99 M/h a. Determine the orders with respect to the two reactants and write the rate law for the reaction b. Calculate the value of the rate constant and include the units of the rate constant Page10 10
3. Initially, 0.200 mol of HI is placed in a 5.00 L flask. The following equilibrium is established: 2HI(g) H2 (g)+ I2(g). Once equilibrium is established, the flask was found to contain 0.124 mol of HI. Calculate the equilibrium concentrations of H2 & I2 and the equilibrium constant, K. 4. Boric Acid ( monoprotic acid of type HA with Ka = 5.0 x 10-5 ) is titrated against 0.200 M NaOH(aq). a. Calculate the ph after 20.0 ml of 0.200 M NaOH(aq) has been added to 50.0 ml of 0.200M boric acid. b. Calculate the ph at the equivalence point. Page11 11
5. Consider the reaction: I2(g) + Cl2(g) 2ICl(g); Kp = 81.9 at 25 C. Calculate the standard free energy change for this reaction. 6. a. Balance the following equation in acidic solution. b. Identify the reducing agent and the oxidizing agent. Cu + NO3 - NO + Cu 2+ ( acidic solution) Page12 12
Key Part 1 1. A 2. C 3. C 4. E 5. E 6. B 7. C 8. B 9. D 10. D 11. A 12. C 13. A 14. B 15. D 16. D 17. D 18. C 19. E 20. A 21. B 22. D 23. D 24. D 25. E 26. D 27. A 28. A 29. C 30. E 31. B 32. C 33. C 34. C 35. A Part II 1. 1.75 10 4 g/mol 2. rate =k [X] [Y]; k= 8.4 M 1 h 1 3. 0.0076 M; 0.0939 4. a. 4.12; b. 8.65 5. 10.9 kj 6. 3Cu + 8H + + 2NO3-2NO + 4H2O +3Cu 2+ Oxidizing agent = Cu; Reducing agent = NO3 - Page13 13