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Unformatted text preview: In recitation, you studied the electrochemistry involved in the "fruit clock". If an orange is used to power the fruit clock, which of the following statements is TRUE ? a. Free electrons flow through the orange to maintain electrical neutrality. b. The orange allows the Zn 2+ and Cu 2+ ions produced in the reaction to mix thereby maintaining electrical neutrality. c. The orange functions as the anode. d. The orange functions as the salt bridge by maintaining electrical neutrality. e. The acids present in the orange are oxidized at the anode to produce hydrogen gas. Which of the following reactions IS a reduction-oxidation reaction? a. formation of N 2 in automobile airbags: 2NaN 3 (s) --> 2Na(l) + 3N 2 (g) b. combustion of propane in a gas grill: C 3 H 8 (g) + 5O 2 (g) --> 3CO 2 (g) + 4H 2 O(g) c. decomposition of hydrogen peroxide (H 2 O 2 ) by light: 2H 2 O 2 (aq) --> 2H 2 O(l) + O 2 (g) d. All of these are reduction-oxidation reactions. e. None of these are reduction-oxidation reactions. Which of the following metals could be used successfully to galvanize iron? a. Ni b. Cu c. Sn d. Co e. Mn Calculate the standard cell potential (in V) for the following reaction at 25 o C. 2Cr(s) + 3Ni 2+ (aq) --> 2Cr 3+ (aq) + 3Ni(s) The layer of zinc on a piece of galvanized iron can be removed by placing it in a concentrated solution of acid. Calculate the standard cell potential (in V) for this reaction. A beaker contains a small amount of gold dust (Au(s)). Which of the following aqueous solutions, when added to the beaker, would dissolve the gold dust (i.e., convert Au(s) to Au 3+ (aq))? a. Cr 2 O 7 2- (acidic solution) b. H 2 O 2 (acidic solution) c. Br 2 d. Zn 2+ e. Al 3+ Which of the following statements best describes what will happen when liquid bromine (Br 2 ) is poured into a beaker containing aluminum metal? a. Br 2 will be reduced; Al will be oxidized b. Br 2 will be oxidized; Al will be reduced c. Br 2 will function as the reducing agent; Al will function as the oxidizing agent d. A reaction will not occur. e. It is impossible to tell. Consider the following galvanic cell reaction at 25 o C, 4Cr 2+ (aq) + O 2 (g) + 4H 3 O + (aq) --> 4Cr 3+ (aq) + 6H 2 O(l) Which of the following statements best describes what would happen to the cell potential if the concentration of Cr 2+ is increased? a. The cell potential would become less positive. b. The cell potential would become more positive. c. The cell potential would remain the same. d. It is impossible to tell. Which of the following half-reactions is involved in the STANDARD HYDROGEN ELECTRODE ? a. Pt 2+ (aq) + 2e---> Pt(s) b. 2H 3 O + (aq) + 2e---> 2H 2 O(l) + H 2 (g) c. H 2 O 2 (aq) + 2H 3 O + (aq) + 2e---> 4H 2 O(l) d. O 2 (g) + 2H 2 O(l) + 4e---> 4OH- (aq) e. None of the above....
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