8_redox_90-02 - Electrochemical Cell < redox/AL90P1_2a 2(a A convenient laboratory method for determining electrode potentials make use of a

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Electrochemical Cell <<< redox/AL90P1_2a 2. (a) A convenient laboratory method for determining electrode potentials make use of a standard hydrogen electrode. Draw a labelled diagram of a hydrogen electrode. What conditions should be maintained when a hydrogen electrode is used as a standard hydrogen electrode? State how these conditions can be met in the laboratory. (6 marks) <<< redox/AL90P2_1b 1. (b) A cell based on the reaction: 6Fe 2+ (aq) + Cr 2 O 7 2- (aq) + 14H + (aq) 6Fe 3+ (aq) + 2Cr 3+ (aq) +7H 2 O(l) consists of one platinum electrode dipped into a beaker containing an acidified solution of K 2 Cr 2 O 7 (aq) and another platinum electrode dipped into a separate beaker containing FeSO 4 (aq), with the two solutions being connected by a salt bridge. With reference to the cell: (i) write balanced equations for the reaction occurring at the cathode and the anode; (ii) state the direction in which electrons move when the electrodes are connected externally; (iii) calculate the e.m.f. of the cell, given that the standard reduction potentials of Fe 3+ /Fe 2+ and acidified Cr 2 O 7 2- /Cr 3+ are respectively +0.77 V and +1.33 V; and (iv) represent the cell using the I.U.P.A.C. convention. (6 marks) <<< redox/AL91P1_2a 2. (a) An electrochemical cell containing an oxygen cathode and a hydrogen anode is shown below. The pistons above the gas chambers are frictionless. (i) Write balanced equations for the half reactions and for the overall reaction in the cell. (ii) How does the concentration of H 2 SO 4 affect the equilibria of the half reactions? (iii) If weights are added to the pistons of both chambers, how would the reading of the voltmeter change? Explain your answer. (5 marks) ALP_topics/redox eq/p.1(12)
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1. (c) (i) Draw a labelled diagram of a cell that makes use of the reaction: 2H 2 SO 4 (aq) + PbO 2 (s) + Pb(s) ---> 2PbSO 4 (s) + 2H 2 O(l) Indicate the direction of electron flow in your diagram. (ii) Write a balanced equation for the reaction at each electrode. (iii) Using the IUPAC convention, write the cell diagram for the above cell. (6 marks) <<< redox/AL94P2_3A 3. (a) The graph below shows the variation in electromotive force(e.m.f.) of the following electrochemical cell with log 10 [Ag + (aq)] at 298 K. Cu(s) Cu 2+ (aq, 1.0 M) Ag + (aq) | Ag(s) Given: At 298 K, for the half-cell Cu 2+ (aq) | Cu(s), E o = + 0.34 V. (i) Using the information from the graph, calculate the standard electrode potential of the half-cell Ag + (aq) | Ag(s) at 298 K. (i i) If the Ag + (aq) solution of the electrochemical cell is replaced by a saturated solution of silver bromate(V) in 0.1 M potassium bromate(V) and the e.m.f. of the cell measured at 298 K is +0.27 V, determine (I) the concentration of Ag + (aq) ions in the saturated solution, and (I I) the solubility product of silver bromate(V) at 298 K. (5 marks)
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This note was uploaded on 08/17/2011 for the course CHEM 100 taught by Professor Fleet during the Fall '08 term at Oxford University.

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8_redox_90-02 - Electrochemical Cell < redox/AL90P1_2a 2(a A convenient laboratory method for determining electrode potentials make use of a

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