Unit 2 Review Questions Over 100 years ago, Gustave Eiffel designed the support structure for the Statue of Liberty. An iron framework was constructed and overlaid with copper sheets in such a way that the copper did not come into direct contact with the iron. 1. The Statue of Liberty s blue- green colour, which has developed over time, can be attributed to the A) oxidation of solid iron into iron (II) ions B) oxidation of solid copper into copper (II) ions C) reduction of solid iron and solid copper into cations D) reduction of oxygen gas and liquid water into hydroxide ions Ethanol reacts with acidified permanganate ion, as represented by the equation 5 C 2H 5OH (l) + 4 MnO 4 - (aq) + 12 H + (aq) - - - > 5 CH 3COOH (aq) + 4 Mn 2+ (aq) + 11 H 2O (l) 2. In this reaction, the oxidation number for the oxidizing agent changes from A) +7 to +2 B) +28 to +8 C) +2 to o D) +10 to 0 3. What is the oxidation number of Mo in CaMoO 4(s) A) +2 B) +4 C) +6 D) - 2 4. Which of the following reducing agents is the strongest? A) I - (aq) B) Br 2(l) C) H 2O (l) D) Al (s) 5. The products in the reaction between Sn 2+ (aq) and Cu 2+ (aq) are A) Cu (s) and Sn (s) B) Cu (s) and Sn 4+ (aq) C) Cu 2+ (aq) and Sn (s) D) Cu 2+ (aq) and Sn 2+ (aq) As2O3(s) + BiO + (aq) + 3 H2O(l) - - - > As(s) + H + (aq) + Bi2O4(s) 6. When the equation is balanced using simplest whole numbers, the coefficient for BiO + (aq) is A) 1 B) 2 C) 3 D) 6
7. At API Grain Processors in Red Deer, Alberta, tanks used in the fermentation of wheat are sterilized using ClO 2(aq). The balanced half- reaction that represents the change that occurs when ClO 2(aq) changes to Cl - (aq) in an acidic solution is A) 2 ClO 2(aq) + 8 H + (aq) - - - > 2Cl - (aq) + 4 H 2O (l) + 6 e - B) ClO 2(aq) + 6 H + (aq) - - - > Cl - (aq) + 3H 2O (l) + 5 e - C) ClO 2(aq) + 4 H + (aq) + 4e - - - - > Cl - (aq) + 2 H 2O (l) D) ClO 2(aq) + 4 H + (aq) + 5e - - - - > Cl - (aq) + 2 H 2O (l) The reactions below involve hypothetical metals and metallic ions. Reaction Observation Z 3+ (aq) + X (s) no evidence of reaction X 2+ (aq) + D (s) evidence of reaction D + (aq) + A (s) evidence of reaction Z 3+ (aq) + D (s) no evidence of reaction A 2+ (aq) + Z (s) no evidence of reaction 8. List the oxidizing agents from strongest to weakest. Use the following information to answer the next question VO2 + (aq) + 2 H + (aq) + e - - - - > VO 2+ (aq) + H2O(l) E = 0.999V VO 2+ (aq) + 2 H + (aq) + e - - - - > V 3+ (aq) + H2O(l) E = 0.340V VO2 + (aq) + 4 H + (aq) + 5e - - - - > V(s) + H2O(l) E = - 0.250 V 3+ (aq) + e - - - - > V 2+ (aq) E = - 0.255 V 9. Which of the following substances is the strongest reducing agent? A) V 2+ (aq) B) V 3+ (aq) C) VO 2 + (aq) D) VO 2+ (aq) 10. Which of the following is not an example of oxidation? A) corrosion of metals B) plating of metals C) rusting of iron D) reaction at the anode of the battery Nova Chemicals is a major producer of ethene in Alberta. Ethene is produced by thermally cracking ethane that has been separated from natural gas. The following equation represents te cracking process C 2H 6(g) - - - > C 2H 4(g) + H 2(g) 11. In the cracking process the oxidation number of A) carbon changes from - 2 to - 3 B) carbon changes from - 3 to - 2 C) hydrogen changes from 0 to +1 D) hydrogen increases and decreases
Four Reaction Equations Key In (s) + La 3+ (aq) - - > no reaction 1 In (s) 5 In 3+ (aq) Np (s) + La 3+ (aq) - - > Np 3+ (aq) + La (s) 2 Np (s) 6 Np 3+ (aq) Np (s) + Nd 3+ (aq) - - > Np 3+ (aq) + Nd (s) 3 Nd (s) 7 Nd 3+ (aq) La (s) + Nd 3+ (aq) - - > no reaction 2 La (s) 8 La 3+ (aq) 12. Arranged in order from weakest to strongest, the oxidizing agents above are,,, and 13. In the reaction 2 Fe 2+ (aq) + Br 2(l) - - > 2 Fe 3+ (aq) + Br - (aq), the Fe 2+ (aq) A) gains electrons and undergoes reduction B) gains electrons and undergoes oxidation C) loses electrons and undergoes reduction D) loses electrons and undergoes oxidation Sn 4+ (aq) + 2 Cr 2+ (aq) - - > Sn 2+ (aq) + 2 Cr 3+ (aq) 14. At standard conditions, the net potential for the reaction represented by the equation above is V. 15. Which of the following characteristics is associated with a voltaic cell consisting of standard half cells of nickel and zinc? A) The E cell = +1.02 V B) cations migrate to the zinc electrode C) oxidation occurs at the nickel electrode D) The net ionic equation is Ni 2+ (aq) + Zn (s) - - - > Ni (s) + Zn 2+ (aq) 16. A student constructed a standard electrochemical cell by using copper metal and a copper (II) nitrate solution in one half cell, and an unlabelled metal and a nitrate solution in the other half cell. The two half c ells were connected by a voltmeter, which registered 0.79 V. If the copper electrode was the cathode, then the unlabelled metal electrode was likely A) tin B) iron C) silver D) chromium 17. The concentration of Sn 2+ (aq) ions in a solution could most quickly and accurately be determined in a high school laboratory by performin A) a redox titration B) an acid- base titration C) a precipiation reaction D) a calorimetry experiment 18. A current of 12.0A is used in the electrolysis of molten sodium chloride. The time required to produce 1.00 kg of Na (l) is A) 2.23 h B) 48.6 h C) 97.2 h D) 194 h
18. The gas formed near electrode 2 is most likely A) I 2(g) B) Na (g) C) O 2(g) D) H 2(g) Use the following information to answer the next two questions. 19. The reaction that would take place at the anode in the electroplating cell above is A) Ni (s) - - > Ni 2+ (aq) + 2e - B) Ni 2+ (aq) + 2e - - - - - > Ni (s) C) Cu (s)- - - > Cu 2+ (aq)+ 2e - D) SO 4 2- (aq) + H 2O (l) + 2e - - - > SO 3 2- (aq) + 2 OH - (aq) 20. In the third step of the electroplating process, the bumper is transferred to a tank that contains CrSO 4(aq). A current of 3750 A is used to plate a thin layer of chromium over the nickel. If the mass of the chromium layer is 125 g, then the time required for the plating process to occur is A) 0.515 min B) 1.03 min C) 2.06 min D) 124 min
21. The anode of the cell is A) Ag (s) B) Zn (s) C) Ag 2O (s) D) Zn(OH) 2(s)