GENERAL CHEMISTRY II CHM202 Unit 4 Practice Test This test is intended to help you get acquainted with the types of questions you will be asked on the Unit Test administered at the end of the unit. The answers are included at the end of the test. Do not pass in your answers to this test. This is optional and will not be graded. Feel free to seek any help you wish on these questions. A mastery of the topics covered in them will assure a good performance on the tests that count. THIS IS NOT THE TAKE HOME TEST. DO NOT PASS IN AN ANSWER SHEET FOR THIS TEST. 1. Which response includes all of the following processes that are accompanied by an increase of entropy? A) I and III B) II and III C) I, II and III D) II only E) III only 2. Which of the following processes would be accompanied by a decrease in entropy? A) H 2 O(s) H 2 O(g) B) H 2 O(l) H 2 O(g) C) H 2 O(s) H 2 O(l) D) H 2 O(g) H 2 O(s) E) H 2 O(l, 50 C) H 2 O(l, 75 C) 3. Determine ΔS for the reaction SO 3 (g) + H 2 O(l) H 2 SO 4 (l). A) 169.2 J/K mol B) 1343.2 J/K mol C) 169.2 J/K mol D) 29.4 J/K mol E) 29.4 J/K mol 4. Which of the following is consistent with an exothermic reaction that is spontaneous at all temperatures? A) ΔH > 0, ΔS < 0, ΔG < 0 B) ΔH > 0, ΔS > 0, ΔG < 0 C) ΔH < 0, ΔS < 0, ΔG < 0 D) ΔH < 0, ΔS > 0, ΔG < 0 E) ΔH > 0, ΔS < 0, ΔG > 0 5. HI has a normal boiling point of 35.4 C, and its ΔH vap is 21.16 kj/mol. Calculate the molar entropy of vaporization (ΔS vap ). A) 598 J/K mol B) 68.6 J/K mol C) 75.2 J/K mol D) 0.068 J/K mol E) 89.0 J/K mol
6. Which of the following is consistent with a reaction at equilibrium? A) ΔG = 0, Q = K B) ΔG = 0, Q > K C) ΔG > 0, Q = K D) ΔG < 0, Q = K E) ΔG = 0, Q < K 7. Hydrogen peroxide (H 2 O 2 ) decomposes according to the equation H 2 O 2 (l) H 2 O(l) + 1 / 2 O 2 (g). Calculate K p for this reaction at 25 C. (ΔH = 98.2 kj/mol, ΔS = 70.1 J/K mol) A) 1.3 10 21 B) 20.9 C) 3.46 10 17 D) 7.5 10 20 E) 8.6 10 4 8. Nitrosyl chloride (NOCl) decomposes at elevated temperatures according to the equation 2NOCl(g) 2NO(g) + Cl 2 (g). Calculate K p for this reaction at 227 C. (ΔH = 81.2 kj/mol, ΔS = 128 J/K mol) A) 1.59 10 2 B) 2.10 10 7 C) 62.8 D) 4.90 10 6 E) 3.20 10 9 9. Find the temperature at which the reaction N 2 O 4 (g) 2NO 2 (g) will be in equilibrium when both gases are present at partial pressures of 1.00 atm. A) 300 C B) 28 C C) 55 C D) 32 C E) 562 C 10. Using the thermodynamic data provided below, calculate the standard change in entropy when one mole of sodium nitrate is dissolved in water. Will the solubility of sodium nitrate increase or decrease if the temperature of the system is increased? A) 90.4 J/K mol; solubility decreases with increasing temperature B) 90.4 J/K mol; solubility increases with increasing temperature C) 90.4 J/K mol; solubility decreases with increasing temperature D) 90.4 J/K mol; solubility increases with increasing temperature E) None of the above
11. Select True or False: For the reaction H 2 O 2 (g) H 2 O(g) + 1 / 2 O 2 (g), ΔH = 106 kj/mol and ΔS = 58 J/K mol at 25 C. H 2 O 2 (g) is spontaneous at 25 C. A) True B) False 12. Complete and balance the following redox equation. When properly balanced using the smallest whole-number coefficients, the coefficient of S is H 2 S + HNO 3 S + NO (acidic solution) A) 1. B) 2. C) 3. D) 5. E) 6. 13. Complete and balance the following redox equation using the set of smallest whole-number coefficients. Now sum the coefficients of all species in the balanced equation. (Remember the coefficients that are equal to one.) The sum of the coefficients is BrO 3 (aq) + Sb 3+ (aq) Br (aq) + Sb 5+ (aq) (acidic solution) A) 4. B) 12. C) 13. D) 17. E) None of these. 14. Determine the cell diagram for the reaction below. Assume platinum electrodes are used when no other solid is present. Cl 2 (g) + Sn 2+ (aq) Sn 4+ (aq) + 2Cl - (aq) A) Pt(s) Cl 2 (g) Cl - (aq) Sn 2+ (aq), Sn 4+ (aq) Pt(s) B) Pt(s) Sn 2+ (aq), Sn 4+ (aq) Cl 2 (g) Cl - (aq) Pt(s) C) Pt(s) Sn 4+ (aq), Sn 2+ (aq) Cl - (aq) Cl 2 (g) Pt(s) D) Pt(s) Cl - (g) Cl 2 (aq) Sn 4+ (aq), Sn 2+ (aq) Pt(s) E) Pt(s) Cl 2 (g) Sn 2+ (aq) Sn 4+ (aq), Cl - (aq) Pt(s) 15. A galvanic cell has the overall reaction: 2Fe(NO 3 ) 2 (aq) + Pb(NO 3 ) 2 (aq) 2Fe(NO 3 ) 3 (aq) + Pb(s) Which is the half reaction occurring at the cathode? A) NO - 3 (aq) + 4H + (aq) + 3e - NO(g) + 2H 2 O(l) B) NO - 3 (aq) + 2H + (aq) + e - NO 2 (g) + H 2 O(l) C) Fe 2+ (aq) Fe 3+ (aq) + e - D) Pb 2+ (aq) + 2e - Pb(s) E) Fe 2+ (aq) + e - Fe 3+ (aq)
16. Calculate the standard cell emf for the following cell: Mg Mg 2+ NO 3 (acid soln) NO(g) Pt A) 3.33 V B) 1.41 V C) 1.41 V D) 8.46 V E) 8.46 V 17. An electrochemical cell based on the following reaction has a standard cell voltage (E cell ) of 0.48 V: Sn(s) + Cu 2+ (aq) Sn 2+ (aq) + Cu(s) What is the standard reduction potential of tin(ii)? (E (Cu 2+ /Cu) = 0.34 V) A) 0.14 V B) 0.14 V C) 0.82 V D) 0.82 V E) none of these 18. Consider the following standard reduction potentials in acid solution: The strongest reducing agent among those shown above is A) Fe 3+. B) Fe 2+. C) Br. D) Al 3+. E) Al. 19. For the electrochemical cell, Fe(s) Fe 2+ (aq) Cu 2+ (aq) Cu + (aq) Pt(s), determine the equilibrium constant (K eq ) at 25 C for the reaction that occurs. A) 1.6 x 10-10 B) 8.6 x 10 19 C) 1.2 x 10-20 D) 9.3 x 10 9 E) 1.3 x 10-5 20. Calculate the cell emf for the following reaction at 25 C: Ni(s) + 2Cu 2+ (0.010 M) Ni 2+ (0.0010 M) + 2Cu + (1.0 M) A) 0.40 V B) 0.43 V C) 0.43 V D) 0.34 V E) 0.37 V
21. Which one of the following is consistent with a galvanic cell? A) ΔG < 0, E cell > 0, Q < K B) ΔG < 0, E cell < 0, Q < K C) ΔG < 0, E cell < 0, Q > K D) ΔG > 0, E cell < 0, Q < K E) ΔG > 0, E cell < 0, Q > K 22. Select True or False: Under acidic conditions, the correctly balanced redox reaction for ClO 2 - (aq) ClO2 (g) + Cl - (aq) is: 5ClO 2 - (aq) + 4H + (aq) 4ClO2 (g) + Cl - (aq) + 2H 2 O(l) A) True B) False Answers 1. A 2. D 3. C 4. D 5. E 6. A 7. D 8. A 9. C 10. D 11. A 12. C 13. D 14. B 15. D 16. A 17. A 18. E 19. B 20. E 21. A 22. A