CHEM 162A Final Exam - Winter Qtr 2004, Exams of Chemistry

Download CHEM 162A Final Exam - Winter Qtr 2004 and more Exams Chemistry in PDF only on Docsity! 1 CHEM 162A FINAL EXAM Winter Qtr 2004 Monday, March 15, 2004 Name: TA Section: Student Number: TA Name: Score (page) 1______, 2______, 3______, 4_____ 5_____ 6 _______ 7_________ Score (page) 8______, 9______, 10______, 11_______ 12 ________TOTAL __________ The periodic table and other information are provided as a separate sheet for your convenience. ANSWER ALL QUESTIONS AND WHERE NECESSARY SHOW YOUR WORK Part I. (100 points) 1. (4 points) True or false: Hydrogen is a nonmetal while lithium is an active metal even though they are in the same group. a) True. Such differences are common for elements in the same group. b) False. Because the elements are in the same group, they have similar metallic qualities. c) True. This can be explained because of the very large difference in atomic radii between hydrogen and lithium. d) False. Both hydrogen and lithium are non-metals e) None of these 2. (4 points) In a given period this group has the element with the smallest ionization energy. a) Group 1A b) Group 2A c) Group 3A d) Group 7A e) Group 8A 3. (6 points) Write a balanced equation for each of the following: (a) the reaction of solid phosphorus pentachloride (PCl5) with water (b) the reaction of liquid phosphorus trichloride (PCl3) with water 2 4. (6 points) Give the formula of each of the following coordination compounds. a) Potassium hexachloroplatinate(II) __________________________________ b) Pentaamminechlorocobalt(III) chloride __________________________________ c) Bis(ethlyenediamine)dinitroiron (III) chloride _____________________________ 5. (4 points) Some transition metals are essential to human health and hence should be a part of one’s diet, except the following: a) Fe b) Mn c) Ni d) Hg e) Zn 6. (4 points) What are the oxidation numbers of the central metal atom in the following coordination compounds? K3[Fe(CN)6], [Cr(NH3)4Br2]Br, [Ni(H2O)6]Cl2, Na2[TaF7] are: a) 3, 3, 3, 5 b) 3, 3, 2, 7 c) –3, 3, 2, 5 d) –3, 1, 2, 5 e) 3, 3, 2, 5 7. (4 points) The complex ions of Zn2+ are all colorless. The most likely explanation for this is: a) Zn2+ is paramagnetic. b) Zn2+ exhibits "d orbital" splittings in its complexes such that they absorb all wavelengths in the visible region. c) Since Zn2+ is a d10 ion, it does not absorb visible light even though the "d orbital" splittings are correct for absorbing visible wavelengths. d) Zn2+ is not a transition metal ion. e) None of these is correct. 8. (7 points) (i) (3 points) Various chromium coordination compounds were found to exhibit diverse colors (violet, blue, green, yellow, purple, etc). True or False: The observed variation in color originates from the transition of electrons between the 3d and 4f orbital energy levels upon absorption of light. ____________________ (ii) (4 points) What is the hybridization of the central metal ion in the following complex ions? a) Co(NH3)63+ ______________ b) Square planar Ni(CN)42_ ______________ 5 15. (12 points) The monomer shown below was reacted by acid-catalyzed condensation polymerization. (a) (6 points) Complete a balanced equation for the polymerization. (b) (3 points) What functional groups are found in the monomer?__________________________ (c) (3 points) What functional group is found in the polymer? ___________________________ Hence what is the generic name of the polymer? ________________________________ 16. (11 points) (i) (4 points) Give the oxidation state of sulfur in: H2SO4 ____________ SF4 _____________ H2S ______________ SCl2 ______________ (ii) (3 points) In terms of the amount of it produced in the world or in the U.S., the number one industrial chemical is: a) HNO3 b) H2SO4 c) N2 d) O2 e) None of these (iii) (4 points) NCl3 and NCl5 are unstable whereas PCl3 and PCl5 are very stable compounds. True or false: Even though the central atoms in all four compounds are group 5A elements, the greater stability of the phosphorus chlorides is explained by the greater atomic size of phosphorus compared to nitrogen. ___________________ HO COOH H+ 6 Part II. (100 points) 17. (15 points) 3. Consider the gas phase reaction at a temperature T. 2NO (g) + Cl2 (g) → 2NOCl (g) The Rate defined as – d[Cl2]/dt was measured at a constant temperature, giving the following results. [NO]o (mol/L) [Cl2]o (mol/L) Initial Rate (mol/L.min) 0.10 0.10 0.18 0.10 0.20 0.36 0.20 0.20 1.45 a. (3 points) What is the rate law? b. (3 points) What is the value of the rate constant? c. (3 points) The order of the reaction with respect to Cl2 is __________ and the overall order or the reaction is _________________ . d. (6 points) It is found that when the original reaction temperature (0.0 oC) was doubled the rate constant increased tenfold. What is the activation energy of the reaction in kJ/mol? 7 18. (10 points) The following reaction mechanism can be assumed to be correct. C4H9Br → C4H9+ + Br- (slow) (1) C4H9+ + H2O → C4H9OH2+ (fast) (2) C4H9OH2+ + H2O → C4H9OH + H3O+ (fast) (3) a. Write the overall balanced equation for the reaction. b. What is the rate law of the overall reaction? c. What is the molecularity of step 1? d. What are the intermediates in the reaction mechanism? e. How will the reaction rate be affected if the initial concentration of C4H9Br is doubled? 19. (12 points) (a) (4 points) Draw the bonding and antibonding MO energy-level diagram for N2+ and show the filling of the orbital with valence electrons. 10 25. (12 points) Consider the phase diagram for compound X shown below. 1 atm P(atm) 0 10 20 30 40 50 60 T (° C) (i) At 25° C and 1 atm X will exist as a: a) solid. b) liquid. c) gas. d) gas/liquid at equilibrium. e) gas/solid at equilibrium. (ii) At 40° C and 0.5 atm X will exist as a: a) solid. b) liquid. c) gas. d) gas/liquid at equilibrium. e) gas/solid at equilibrium. (iii) The normal melting point of X is most likely: a) 13° C b) 47° C c) 18° C d) 0° C e) 29° C (iv) How will the melting point of X change with increased pressure? a) increase b) decrease c) remain the same d) there is not enough information given e) increase and then decrease 11 26. (6 points) (i) In which of the following processes will energy by evolved as heat? a) sublimation b) crystallization c) vaporization d) melting e) none of these (ii) Which of the following processes must exist in equilibrium with the condensation process when a measurement of vapor pressure is made? a) fusion b) evaporation c) sublimation d) boiling e) none of these 27. (9 points) (i) Which of the following statements is true about p-type silicon? a) It is produced by doping Si with P or As. b) Electrons are the mobile charge carriers. c) It does not conduct electricity as well as pure Si. d) All are true. e) None is true. (ii) Doping Te with As would produce a(n) __________ semiconductor with __________ conductivity compared to pure Te. a) n-type, increased b) n-type, decreased c) p-type, increased d) p-type, decreased e) intrinsic, identical (iii) Which of the statements a through d is incorrect? a) Molecular solids have high melting points. b) The binding forces in a molecular solid include London dispersion forces. c) Ionic solids have high melting points. d) Ionic solids are insulators. e) All of the statements a through d are correct. 28. ( 5 points) Rank in order of decreasing atomic radius the following metals: Al, Li, Na, K, and Mg (i.e. A>B>C>D>E, where A is largest and E is smallest). 12 29. ( 2 points) What reason is given for the stability of CC, NN, and OO bonds, compared to the instability of SiSi, PP, and SS bonds? a) Their metallic character varies greatly. b) Large differences in their ionization energies. c) Large differences in their electronegativities. d) Large differences in their abilities to form strong pi bonds. e) None of these.