Practice Test 20.1 (va pg 1 of 5) This is practice - Do NOT cheat yourself of finding out what you are capable of doing. Be sure you follow the testing conditions outlined below. DO NOT USE A CALCULATOR. You may use ONLY the green periodic table for questions 1-29. Work only for 40 minutes. Time yourself. It is important that you practice working for speed. Then when time is up, continue working without a calculator but use a different color writing utensil so you will have a sense of how many you were able to complete under the time constraints and without the calculator. After you have completed as many as possible without the calculator. Change to yet another color utensil and continue with a calculator. Finish or change as many as you can/need to. Consider this reaction: 3Au(s) + 8H +1 + 2NO3-1 3Au +2 (aq) + 2NO(g) + 4H2O(L) Mark each of the following statements (about the reaction above) as true or false. 1. T F Au(s) is reduced during the reaction. 2. T F The oxidation state of nitrogen changes from +6 to +2. 3. T F Hydrogen ions are oxidized when they form H2O(L). 4. T F 8 electrons are lost and 8 electrons are gained during this reaction. 5. Which substance is the oxidizing agent in the following reaction: Cr2O7 2- + 6S2O3 2- + 14H + 2Cr 3+ + 3S4O6 2- + 7H2O a. Cr2O7 2- b. S2O3 2- c. H + d. Cr 3+ e. S4O6 2-9. The half-reaction occurring at the anode in the balanced reaction shown below is 3MnO4-1 + 24H + + 5Fe (s) 3Mn 2+ + 5Fe 3+ + 12H2O a. Mn O4-1 + 8H + + 5e - Mn 2+ + 4H2O MnO4-1 + 12H + + 6e - 2Mn 2+ + 3 H2O c. Fe Fe 3+ + 3e - d. Fe Fe 2+ + 2e - e. Fe 2+ Fe 3+ + e - 6. What is the oxidation number of manganese in the KMnO4 a. +1 b. +2 c. +5 d. +4 e. +7 7. How many electrons appear in the following half-reaction when it is balanced. d. 4 e. 6 Cr2O7 2- + 14H +1 2Cr +3 + 7H2O 8. How many electrons appear in the following half-reaction when it is balanced. a. 6 c. 4 d. 1 e. 3 S4O6 2-2S2O3-2 10. In a voltaic cell, electrons flow from the to the. a. salt bride, anode b. anode, salt bridge c. cathode, anode d. salt bridge, cathode e. anode, cathode 11. The oxidation half reaction occurring in the standard hydrogen electrode is a. H2 2H +1 + 2e - H + + 2OH -1 H2O c. O2 + 4H + + 4e - 2H2O d. 2H + + 2e - H2 e. 2H + + Cl2 2HCl 12. The more the value of E red, the greater the driving force for oxidation. a. positive b. negative c. exothermic d. endothermic e. extensive
Practice Test 20.1 (va pg 2 of 5) 13. Given the following half reactions: Sn 4+ + 2e- Sn 2+ Fe 3+ + 1e- Fe 2+ Eº = 0.15 V Eº = 0.77 V Determine the standard cell potential (E cell) for the voltaic cell based on the reaction a. +0.47 V b. +0.62 V c. +0.92 V d. +1.39 V e. +1.69 V Sn 2+ + 2Fe 3+ 2Fe 2+ + Sn 4+ 14. When this reaction is balanced, the coefficient on the Sn +2 is. d. 4 e. 6 Sn 4+ + Cr Cr 3+ + Sn 2+ 15. The relationship between the change in Gibbs free energy and the emf of an electrochemical cell is given by a. ΔG = 18. The standard cell potential (E cell) for the reaction below is +0.63 V. Determine the emf for this reaction when [Zn 2+ ] = 1.0 M and [Pb 2+ ] = 1.0 10-4 M. a. 0.39 V b. 0.51 V c. 0.63 V d. 0.75 V e. 0.87 V Pb 2+ + Zn Zn 2+ + Pb 19. The reaction for the automobile lead/acid battery is shown below. The lead-containing reactant(s) consumed during recharging of a lead-acid battery is/are PbO2(s) + Pb(s) + 2HSO4-2 (aq) + 2H +1 2PbSO4(s) + 2H2O a. Pb only b. PbO2 only c. PbSO4 only d. both PbO2 and PbSO4 e. both Pb and PbO2 20. How long will it take to plate out 2.19 g of chromium metal from a solution of Cr 3+ using a current of 35 amps in an electrolyte cell? a. (2.19)(95,500)(52)(3) (35) b. ΔG = c. ΔG = -nfe d. ΔG = -nrtf e. ΔG = 16. The standard cell potential (E cell) of the reaction below is +0.126 V. The value of G for the reaction is Pb (s) + 2H + (aq) Pb 2+ (aq) + H2 (g) b. c. d. e. (2.19)(35)(52) (96,500)(3) (35)(52) (96,500)(3)(2.19) (2.19)(96,500)(3) (52)(35) (3)(96,500) (52)(35)(2.19) a. -24,318 kj b. +24,318 kj c. -24.3 kj d. +24.3 kj e. -12.1 kj 17. Which transformation could take place at the anode of an electrochemical cell? a. Cr2O7-2 Cr +2 b. F2 to F -1 c. O2 to H2O d. HAsO2 to As e. None of the above could take place at the anode. 21. What mass of Ca metal is produced by the electrolysis of molten CaBr2 using a current of 30.0 amp for 10.0 hours a. b. c. d. e. (600)(40)(30) (96,500) (30)(600)(40) (96,500)(2) (30)(10)(40) (96,500)(2) (30)(600)(2) (40)(96,500) (2)(96,500) (30)(10)(40)
Practice Test 20.1 (va pg 3 of 5) 22. Which of the following reactions is a redox reaction? i. K2CrO4 + BaCl2 BaCrO4 + 2KCl ii. iii. a. i. only b. ii. only c. iii. only d. i. and iii. e. ii. and iii. Pb 2+ + 2Br 1- PbBr2 Cu + S CuS 23. Which one of the following reactions is a redox reaction? a. NaOH + HCl NaCl + H2O b. Pb 2+ + 2Cl -1 PbCl2 c. AgNO3 + HCl HNO3 + AgCl d. 2HC2H3O2 + Ca(OH)2 2H2O+ Ca(C2H3O2)2 e. None of the above are redox reactions. 24. Which substance is the reducing agent in the following reaction? Fe2S3 + 12HNO3 2Fe(NO3)3 + 3S + 6NO2 + 6H2O a. HNO3 b. S c. NO2 d. Fe2S3 e. H2O 27. Consider the half reactions shown below to answer the following question: Fe 3+ + 1e- Fe 2+ Sn 4+ + 2e- Sn 2+ Fe 2+ + 2e- Fe Cr 3+ + 3e- Cr Eº = 0.77 V Eº = 0.15 V Eº = -0.44 V Eº = -0.74 V Which of the following reactions will occur spontaneously as written? a. Sn 4+ + Fe 3+ Sn 2+ + Fe 2+ b. 3Fe + 2Cr 3+ 2Cr + 3Fe 2+ c. Sn 4+ + Fe 2+ Sn 2+ + Fe d. 3Sn 4+ + 2Cr 2Cr 3+ + 3Sn 2+ e. 3Fe 2+ Fe + 2Fe 3+ 28. Consider an electrochemical cell based on the reaction: 2H + + Sn Sn 2+ + H2 Which of the following actions would not change the measured cell potential? a. lowering the ph in the cathode compartment b. addition of more metallic tin to the anode compartment c. increasing the tin(ii) ion concentration in the anode compartment d. increasing the pressure of hydrogen gas in the cathode compartment e. All of the above will change the measured cell potential. 25. What is the coefficient of the permanganate ion when the following equation is balanced? MnO4-1 + Br -1 Mn +2 + Br2 d. 5 e. 4 (acidic solution) 26. It is possible to produce elemental iodine by electrolyzing any of these iodine-containing compounds under the proper conditions. Which compound will require the most coulombs to produce one mole of iodine? a. MgI2 b. KIO c. Ba(IO2)2 d. Al(IO3)3 e. NaIO4 29. A concentration cell is constructed with two silver electrodes, where the half-reaction is AgCl(s) + e -1 Ag(s) + Cl -1 (aq) E = +0.222 V The concentrations of chloride ion in the two compartments are 0.0222 M and 2.22 M. Determine the cell emf. a. 0.212 V b. 0.118 V c. 0.00222 V d. 22.2 V e. 0.232 V 30. What mass of aluminum will be plated when 0.10 faraday is passed through out of an aqueous solution of aluminum sulfate. a. 0.45 g b. 0.90 g c. 2.7 g d. 8.0 g e. 16 g
Practice Test 20.1 (va pg 4 of 5) Use your blue reduction charts to answer the following two questions. 31. Which of the halogens is the strongest oxidizing agent? a. Cl2 b. Br2 c. F2 d. I2 e. All of the halogens have equal strength as oxidizing agents. 32. Using your Eº reduction chart, which substance can oxidize I -1 to I2? a. Br2 b. Ag c. Cu 2+ d. Ni 2+ e. Br -1 33. Balance the following redox reaction in a basic solution and answer the questions below Cr2O7-2 + CH3OH H2CO2 + Cr +3 a. Which element is reduced? b. Which species is the reducing agent? c. What is the number of electrons transferred? d. What might color changes might you observe during the reaction
Practice Test 20.1 (va pg 5 of 5) 1 F 2 F 3 F 4 F 5 a 6 e 7 e 8 b 9 c 10 e 11 a 12 b 13 b 14 c 15 c 16 c 17 e 18 b 19 c 20 d 21 b 22 c 23 e 24 d 25 b 26 e 27 c 28 b 29 b 30 b 31 a 32 Cr 33 CH3OH 34 You would see a color change. Dichromate, Cr2O7-2 is orange and all the products are colorless.