Unit 4 Exam, Spring 2018 (Electrochemistry & Nuclear Chemistry)

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1 Chem 401 (Nuss) Name: Unit 4 Exam, Spring 2018 (Electrochemistry & Nuclear Chemistry) Seat # Lab Day DO NOT REMOVE THIS PAGE FROM YOUR TEST BOOKLET! The time allotted for this exam is 80 minutes. Be sure to note which test number you have and to write it down on your Scantron form. Show all of your work directly on this exam packet. Transfer the letter code for the correct answer to the multiple choice questions to your Scantron form. Box your answer to the free response problems. Be sure to express your answers to the correct number of significant figures and to include the proper units where appropriate. Standard Reduction Potentials Reduction Reaction E red (V) Reduction Reaction E red (V) Li + + e Li H e H K + + e K Cu e Cu Mg e Mg Cu + + e Cu Al e Al I2 + 2 e 2 I SO4 2 + H2O + 2 e SO OH Ag + + e Ag H2O + 2 e H2 + 2 OH (-0.41V in H2O) Hg e Hg Zn e Zn Hg e Hg Fe e Fe Br2 + 2 e 2 Br 1.07 Sn e Sn O2 + 4 H e 2 H2O (0.82V in H2O) Pb e Pb Cl2 + 2 e 2 Cl 1.36 Fe e Fe F2 + 2 e 2 F 2.87

2 Exam 4 (Electrochemistry & Nuclear Chemistry) Spring 2018 Name Seat Lab Day MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. (3 pts ea) 1) Assign the oxidation state of each atom in potassium chlorate, KClO 3. A) K = -1, Cl = +1, O = 0 B) K = +1, Cl = +1, O = -2 C) K = +1, Cl = +5, O = -2 D) K = +1, Cl = -1, O = 0 E) K = -1, Cl = -1, O = +2 2) In the following reaction, Zn (s) + CuSO4 (aq) ZnSO4 (aq) + Cu (s) A) CuSO4 is the reducing agent and Zn is the oxidizing agent. B) ZnSO4 is the reducing agent and Cu is the oxidizing agent. C) Cu2+ is the reducing agent and Zn2+ is the oxidizing agent. D) Zn is the reducing agent and Cu2+ is the oxidizing agent. E) none of the above 3) Determine the cell notation for the redox reaction given below. Sn(s) + 2 Ag+(aq) Sn2+(aq) + 2 Ag(s) A) Sn(s) Sn2+(aq) Ag+(aq) Ag(s) B) Ag(s) Ag+(aq) Sn2+(aq) Sn(s) C) Sn2+(aq) Sn(s) Ag(s) Ag+(aq) D) Ag+(aq) Ag(s) Sn(s) Sn2+(aq) E) Sn(s) Ag(s) Sn2+(aq) Ag+(aq) 4) Determine which of the following pairs of reactants will result in a spontaneous reaction at 25 C. A) Sn2+(aq) + Pb(s) B) Pb2+(aq) + Cu(s) C) Mg2+(aq) + Sn(s) D) H2(g) + Cu2+(aq) E) None of the above pairs will react. 5) Use the standard half-cell potentials listed below to calculate the standard cell potential for the following reaction occurring in an electrochemical cell at 25 C. (The equation is balanced.) 3 Cl2(g) + 2 Fe(s) 6 Cl (aq) + 2 Fe3+(aq) Cl2(g) + 2 e 2 Cl (aq) Fe3+(aq) + 3 e Fe(s) E = V E = V A) V B) V C) V D) V E) V A-1

3 6) From the activity list included in this problem, which element/ion listed below is the strongest oxidizing agent? Activity Series Sn2+(aq) + 2e- Sn(s) Pb2+(aq) + 2e- Pb(s) Eo v v 2H+(aq) + 2e- H 2(g) 0.000v Cu2+(aq) + 2e- Cu(s) 0.337v A) Sn(s) B) Cu+2 C) Pb D) Sn+2 E) Cu(s) 7) How many electrons are transferred in the following reaction? (The reaction is unbalanced.) Mg(s) + Al3+(aq) Al(s) + Mg2+(aq) A) 6 B) 4 C) 3 D) 1 E) 2 8) Which of the following reactions would have the largest value of K at 298 K? A) A + B 3 C; E cell = V B) A + 2 B C; E cell = V C) A + B C; E cell = V D) A + B 2 C; E cell = V E) More information is needed to determine. 9) Which battery system is based on half reactions involving zinc metal and manganese dioxide? A) Ni-Cad batteries B) dry-cell batteries C) fuel cells D) car batteries E) none of the above 10) An electrolysis is carried out by passing an electric current through a solution of copper (I) fluoride using inert electrodes. This causes: A) H2 to form at the negative electrode B) oxygen to form on the negative electrode C) Cu to plate out on the anode D) fluorine to form on the positive electrode E) Cu to plate out on the negative electrode 11) Choose the INCORRECT statement. A) Electrolytic cells are cells where electron flow is caused by spontaneous reactions. B) A double vertical line separates half cells in a cell diagram. C) A single vertical line separates phases in a cell diagram. D) A voltaic cell is a galvanic cell. E) Voltaic cells produce an electron flow. A-2

4 12) During the electrolysis experiment where a nail was galvanized with zinc, which of the following is TRUE? A The zinc is a passive electrode and the nail is an active electrode. B The zinc is an active electrode and the nail is a passive electrode. C They are both active electrodes. D They are both passive electrodes. A) B) C) D) 13) Identify the missing particle in the following nuclear equation: Th 4 2 He +? A) Ac B) Ac C) U D) Ra E) Ra 14) Determine the identity of the daughter nuclide from the beta decay of P. A) Al B) P C) S D) Si E) S 15) Determine the identity of the daughter nuclide from the positron emission of 11 6 C. A) 10 5 B B) 11 7 N C) N D) B E) 5 6 C 16) Determine the identity of the daughter nuclide from the electron capture by Rb. A) Sr B) Kr C) Br D) Y E) Kr 17) An isotope which has too high a neutron-proton ratio can gain stability by: A) alpha emission B) gamma emission C) positron emission D) electron capture E) beta emission 18) Which of the following statements are TRUE? A) Beta radiation has the highest ionizing power (damage potential) of any radioactivity. B) Gamma rays have the lowest ionizing power (damage potential) of any radioactivity. C) Beta emitters will do more damage than alpha emitters within the body. D) Alpha radiation has the highest penetrating power of any radioactivity. E) None of the above are true. A-3

5 19) Write a nuclear equation to describe the spontaneous fission of 244 Am to form I-134 and Mo-107. Determine 95 how many neutrons are produced in the reaction. A) 1 B) 0 C) 2 D) 4 E) 3 20) Above what atomic number are there no stable isotopes of any element? A) 92 B) 20 C) 83 D) 89 E) 40 21) Consider the fission of U-235. If sufficient fissionable material, known as the, is contained in a small enough volume, a sustained chain reaction can result. A) mass deficiency B) nuclear mass C) critical mass D) fission mass E) None of the above are true. 22) The chance of an isotope being stable is greatest if the numbers of A protons and nuetrons are both even B protons and neutrons are both odd C protons are odd and neutrons are even D protons are even and neutrons are odd A) B) C) D) 23) The nuclide As-76 has a half-life of 26.0 hours. If a sample of As-76 weighs 344 g, what mass of As-76 remains after 538 minutes? A) 271 g B) 144 g C) 251 g D) 67.8 g E) 437 g 24) Fluorine-18 undergoes positron emission with a half-life of 1.10 x 102 minutes. If a patient is given a 248 mg dose for a PET scan, how long will it take for the amount of fluorine-18 to drop to 83 mg? (Assume that none of the fluorine is excreted from the body.) A) 134 min B) 99 min C) 213 min D) 174 min E) 300. min A-4

6 25) What mass of aluminum can be plated onto an object in 755 minutes at 5.80 A of current? A) 220. g B) 24.5 g C) 147 g D) 73.5 g E) 8.17 g 26) Use the tabulated half-cell potentials to calculate DG for the following balanced redox reaction in kj. Pb2+(aq) + Cu(s) Pb(s) + Cu2+(aq) A) +89 kj B) -21 kj C) +46 kj D) -41 kj E) kj FREE RESPONSE. 27) The following experiments were performed and the observations logged. - A strip of Q was placed in a soln of Y+ No Reaction - A strip of Q was placed in a solution of Z3+ A ppt forms - A strip of Z was placed in a solution of Y+ No Reaction - A strip of X was placed in a solution of Z3+ No Reaction Place the 4 metals in an activity series.(3 pts) highest activity lowest activity A-5

7 28) Calculate the cell potential for the following reaction that takes place in an electrochemical cell at 25 C. (5pts) Sn(s) Sn2+(aq, 1.8 M) Ag+(aq, M) Ag(s) 29) Determine the binding energy of an O-16 nucleus in J/nucleon. The O-16 nucleus has a mass of amu. A proton has a mass of amu, a neutron has a mass of amu. (5pts) A-6

8 30) If the radioactive decay from a gamma emitting source is measured to be 822cpm using a detector that is 7.0cm away from the source. At what distance would the measured radiation drop to 20% of the original value? (4pts) 31) Assign oxidation numbers to all atoms in the following unbalanced reaction. Next, balance it in basic solution. (5pts) Show the individual balanced half reactions and all of your work to get to the final overal balanced reaction. MnO4 - (aq) + Br- (aq) MnO2(s) + BrO3 - (aq) balanced oxid. 1/2 rxn: balanced red. 1/2 rxn: A-7

9 32) Extra Credit: The half-life of 238U, which decomposes to 206Pb, is y. A rock contains 50.0g each of these two isotopes. How old is this rock? (5 pts) A-8

2. Balance the following reaction. How many electrons would be transferred?

2. Balance the following reaction. How many electrons would be transferred? JASPERSE CHEM 210 Ch. 19 Electrochemistry PRACTICE TEST 4 VERSION 3 Ch. 20 Nuclear Chemistry 1 Formulas: E cell =E reduction + E oxidation G = nfe cell (for kj, use F = 96.5) E cell = E [0.0592/n]log Q