Fall2008 Exam - Final - partial key

# Fall2008 Exam - Final - partial key - Be sure to show your...

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1 Be sure to show your work and give the proper units in the answer. Any problems that have answers without supporting work will only receive half credit. You can use the back side of these sheets if additional space is required (make a note in the problem if you do this). Section I. (113pts total) Be sure to read each question completely before you begin the answer it. In general, this section contains simple concept based questions that have few calculations. 1.1 (2pts) The half-reaction that occurs at the cathode during electrolysis of an aqueous CuCl 2 solution is Answer=__________________Cu 2+ + e - Cu + .<-- 1.2 (2pts) Consider the following reaction: 2Fe 2+ (aq) + Cu 2+ 2Fe 3+ (aq) + Cu. When the reaction comes to equilibrium, what is the cell voltage? Answer=__________________ A. 0 V.<-- 1.3 (2pts) How many coulombs of charge are required to cause reduction of 0.20 mole of Cr 3+ to Cr? Answer=__________________ A. 5.8 × 10 4 C<-- 1.4 (2pts) Many different ways have been proposed to make batteries. One cell is set up with copper and lead electrodes in contact with CuSO 4 (aq) and Pb(NO 3 ) 2 (aq), respectively. If the Pb 2+ and Cu 2+ concentrations are each 1.0 M, what is the overall cell potential? Answer=__________________0.56 V <-- 1.5 (6pts) Complete and balance the following redox equation. H 2 S + HNO 3 S + NO (acidic solution) H 2 O +MnO 4 - + I - MnO 2 + IO 3 - (basic solution) BrO 3 - (aq) + Sb 3+ (aq) Br - (aq) + Sb 5+ (aq) (acidic solution) 1.6 (2pts) Given the following notation for an electrochemical cell Pt(s) | H 2 (g) | H + (aq) || Ag + (aq) | Ag(s), what is the balanced overall (net) cell reaction? E. H 2 (g) + 2Ag + (aq) 2H + (aq) + 2Ag(s) <--

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2 1.7 (2pts) For the reaction, 2Cr 2+ + Cl 2 (g) 2Cr 3+ + 2Cl - , E ° cell is 1.78 V. Calculate E ° cell for the related reaction Cr 3+ + Cl - Cr 2+ + (1/2)Cl 2 (g). Answer=__________________ C. -1.78 V<-- 1.8 (2pts) A molecule or ion that provides an electron pair for coordinate covalent bond formation is called a Lewis ________. base 1.9 (2pts) A molecule or atom that accepts an electron pair to form a coordinate covalent bond is called a Lewis _______. acid 1.10 (2pts) The coordination number of cobalt in [Co(NH 3 ) 6 ]Cl 3 is _______.6 1.11 (2pts) In the complex ion [ML 6 ] n+ , M n+ has six d electrons and L is a weak field ligand. According to crystal field theory, the magnetic properties of the complex ion correspond to how many unpaired electrons? _________. E. 4 1.12 (2pts) Which of these electron energy level patterns would absorb light with the shortest wavelength? ___________. D. D 1.13 (2pts) The number of unpaired electrons in the [CrCl 6 ] 4- ion is _________.4 1.14 (2pts) Write the chemical formula of diamminedichloroplatinum(II). Pt(NH 3 ) 2 Cl 2 1.15 (2pts) Name the complex ion [Co(H 2 O) 4 Cl 2 ] + . tetraaquodichlorocobalt(III) ion 1.16 (10pts) Answer the following questions regarding the figure below assuming that both electrodes are made of zinc, and that the solution is A is 1.0 M ZnSO 4 and the solution in B is 0.01M ZnSO 4 . E cell =______________ E cell =______________ Is the reaction sponanteous?___________________ Which side is the anode (A or B)?________ Draw on the figure the direction of the electron movement 1.17 (8pts) Identify the units of the following : 1st order rate constant =__________________ Zero order rate constant =__________________ 2 nd order rate constant =__________________ decay constant =__________________