CHEM Lab Section Number: Name (printed): Signature: This exam consists of 36 questions all of equal value for a total of 225 points. Make sure that your test has all of the pages. Please read each problem carefully. There are no intentionally misleading questions; each problem should be taken at its face value. Please mark your answers on the Scantron sheet provided to you and on the actual exam. You will be given a periodic table and an exam information sheet to use during the exam. You may remove it from the exam make it more accessible. You may also use the designated Casio fx-300ms-plus calculator or equivalent non-programmable non-graphing scientific calculator during the exam. Use the back pages of the test as scratch paper. You are not allowed to use any devices capable of accessing the internet, textbooks, notes, or homemade reference sheets during the exam. You may leave if you finish the exam early. Give the exam and the information sheet to your TA and leave quietly without disturbing other students. Before leaving, check that all your answers have been properly entered on the Scantron sheet and the exam and that your name is written on every page of the exam and on the Scantron sheet. All cell phones and electronic devices must be turned off and put away. Please remove all hats and caps. Place your books and all papers out of sight under your seat. If the TA believes that you might be looking at your neighbor s paper, you will be asked to move to a new location. Exam scores will be posted on Blackboard as soon as the grading is complete. Your test will be returned to you in the first lab meeting of next week. If you have any questions regarding the grading of your exam, please notify your TA. The time available for the exam is 120 minutes. Good luck! 1 of 9
Name: Lab Section #: Please mark your answers on the scantron sheet using a #2 pencil and also mark your answers on the exam itself. Mark Test From A on your scantron. 1. A system that does no work but which receives heat from the surroundings has: (a) q < 0, ΔE > 0 (b) q > 0, ΔE < 0 (c) q = ΔE (d) q = ΔE (e) w = ΔE 2. A system which undergoes an adiabatic change (i.e., q = 0) and has work done on it by the surroundings has: (a) w = ΔE (b) w = ΔE (c) w > 0, ΔE < 0 (d) w < 0, ΔE > 0 (e) w > ΔE 3. A system receives 575 J of heat and delivers 425 J of work. Calculate the change in the internal energy, ΔE, of the system. (a) 150 J (b) 150 J (c) l000 J (d) 1000 J (e) 575 J 4. A system delivers 1275 J of heat while the surroundings perform 855 J of work on it. Calculate ΔE in J. (a) 2130 J (b) 420 J (c) 420 J (d) 2130 J (e) 1275 J 5. Cold packs, whose temperatures are lowered when ammonium nitrate dissolves in water, are carried by athletic trainers when transporting ice is not possible. Which of the following is true of this reaction? (a) ΔH < 0, process is exothermic (b) ΔH > 0, process is exothermic (c) ΔH < 0, process is endothermic 2 of 9
(d) ΔH > 0, process is endothermic (e) ΔH = 0, since cold packs are sealed 6. Calculate q when 28.6 g of water is heated from 22.0 C to 78.3 C. (a) 0.385 kj (b) 1.61 kj (c) 6.74 kj (d) 9.37 kj (e) 1.61 10 3 kj 7. Ethylene glycol, used as a coolant in automotive engines, has a specific heat capacity of 2.42 J/(g K). Calculate q when 3.65 kg of ethylene glycol is cooled from 132 C to 85 C. (a) 1900 kj (b) 420 kj (c) 99 kj (d) 0.42 kj (e) 4.2 10 6 kj 8. A 275 g sample of nickel at 100.0 C is placed in 100.0 ml of water at 22.0 C. What is the final temperature of the water? Assume that no heat is lost to or gained from the surroundings. Specific heat capacity of nickel = 0.444 J/(g K) (a) 39.6 C (b) 40.8 C (c) 61.0 C (d) 79.2 C (e) 82.4 C 9. A 1.00 g piece of copper metal is initially at 100.0 C. It is dropped into a coffee cup calorimeter containing 50.0 g of water at a temperature of 20.0 C. After stirring, the final temperature of both copper and water is 25.0 C. Assuming no heat losses what is the specific heat capacity of the copper in J/(g K)? (a) 2.79 J/(g K) (b) 3.33 J/(g K) (c) 13.9 J/(g K) (d) 209 J/(g K) (e) none of the above 10. A 2.09 g piece of zinc metal is added to a calorimeter containing 1.50 L of 0.600 M HCl. This results in a reaction where zinc chloride and hydrogen gas is formed, and the temperature of the solution increases by 0.780 C. The density of the solution is 1.00 g/ml, and its specific heat capacity is the same as water, what is the enthalpy change, per mole of zinc, for the reaction? (a) 65.8 kj (b) 2.34 kj 3 of 9
(c) 4.90 kj (d) 153 kj (e) 136 kj 11. What is the final temperature when 20.0 g of water at 25 C is mixed with 30.0 g of water at 80 C? (a) 35 C (b) 42 C (c) 58 C (d) 53 C (e) 70 C 12. The highly exothermic thermite reaction, in which aluminum reduces iron(iii) oxide to elemental iron, has been used by railroad repair crews to weld rails together. What mass of iron is formed when 725 kj of heat are released? 2Al(s) + Fe2O3(s) 2Fe(s) + Al2O3(s) ΔH = 850 kj (a) 47 g (b) 65 g (c) 95 g (d) 112 g (e) 130 g 13. Use Hess's Law to calculate the enthalpy change for the reaction from the following data: WO3(s) + 3H2(g) W(s) + 3H2O(g) 2W(s) + 3O2(g) 2WO3(s) 2H2(g) + O2(g) 2H2O(g) ΔH = 1685.4 kj ΔH = 477.84 kj (a) 125.9 kj (b) 252.9 kj (c) 364.9 kj (d) 1207.6 kj (e) none of the above 14. Use the following data to calculate the standard heat (enthalpy) of formation, ΔHf (298), of manganese(iv) oxide, MnO2(s). 2MnO2(s) 2MnO(s) + O2(g) MnO2(s) + Mn(s) 2MnO(s) ΔH = 264 kj ΔH = 240 kj (a) 504 kj (b) 372 kj (c) 24.0 kj 4 of 9
(d) 24.0 kj (e) 504 kj 15. The compound carbon suboxide, C3O2, is a gas at room temperature. Use the information below to calculate the heat of formation of carbon suboxide. (a) 116.8 kj (b) 93.7 kj (c) 24 kj (d) 24 kj (e) 504 kj 2CO(g) + C(graphite) C3O2(g) ΔH = 127.3 kj/mol ΔHf (298) of CO(g) = 110.5 kj/mol 16. Which one of the following is not a correct formation reaction? (products are correct) (a) H2(g) + O(g) H2O(l) (b) ½H2(g) + ½Cl2(g) HCl(g) (c) 6C(graphite) + 3H2(g) C6H6(l) (d) C(graphite) C(diamond) (e) 6C(graphite) + 6H2(g) + 3O2(g) C6H12O6(s) 17. Which one of the following is a correct formation reaction? (a) C(diamond) C(graphite) (b) H2(g) + O(g) H2O(l) (c) C(graphite) + 4H(g) CH4(g) (d) 6C(graphite) + 6H2O(s) C6H12O6(s) (e) 2C(graphite) + 3H2(g) + ½O2(g) C2H5OH(l) 18. Ethanol, C2H5OH, is being promoted as a clean fuel and is used as an additive in many gasoline mixtures. Calculate the ΔH rxn for the combustion of ethanol in the presence of excess oxygen. (a) 1235 kj (b) 751.1 kj (c) 357.6 kj (d) 357.6 kj (e) 1235 kj Compound C2H5OH(l) CO2(g) H2O(g) ΔHf (298) 277.7 kj/mol 393.5 kj/mol 241.8 kj/mol 19. Of the symbols below, which is used to express Planck s constant? 5 of 9
CHEM 200/202 Fall 2016 Exam 2-A October 22, 2016 (a) V (b) λ (c) P (d) h (e) π Below are the graphical representations of five (numbered) waves. Use those images to answer the following two questions. 1 2 3 4 5 20. Which of the waves in the figure above has the longest wavelength? (a) Wave 1 (b) Wave 2 (c) Wave 3 (d) Wave 4 (e) Wave 5 21. Which of the waves in the figure above has the highest energy? (a) Wave 1 (b) Wave 2 (c) Wave 3 (d) Wave 4 (e) Wave 5 22. The frequency used by devices communicating via Bluetooth is 2.4GHz. What is the energy of radio waves with this frequency? (a) 1.2 10 24 J (b) 1.6 10 24 J (c) 2.8 10 16 J (d) 8.3 10 17 J (e) 1.4 10 35 J 23. Which statement below best describes what was observed measurements were made of Blackbody radiation: (a) That if a wavelength of light had sufficiently high frequency, under the right conditions, it could eject an electron from a piece of metal. 6 of 9
(b) That despite predictions from classical mechanics and electromagnetism, radiation from heated objects had a peak intensity before the intensity decreased at shorter wavelengths. (c) That the emission of light from an excited gas at low pressure results in an emission spectra with a few bright emission lines, and mainly black regions with no emissions. (d) That the orbits of electrons around the nucleus of an atom were in quantized energy levels, and that the electron was moving in these orbits as a standing wave. (e) That firing a stream of electrons at two very closely spaced slits, or at a thin sheet of atoms, will result in a diffraction pattern similar to that seen with light. 24. A series of photoelectric devices have been made, each with a different metal (see table below). If all of the devices are exposed to the same light of 337 nm, which one(s) will successfully demonstrate the photoelectric effect? Metal Calcium Aluminum Gold Uranium Work Function (in J) 4.65 10 19 J 6.54 10 19 J 8.17 10 19 J 5.77 10 19 J (a) Only uranium (b) Only aluminum (c) Gold, aluminum, and uranium (d) Calcium, and uranium (e) Aluminum, uranium, and calcium 25. A hydrogen atom is excited such that its electron is in the n=6 energy level. The electron relaxes down to the n=2 quantum level, emitting a photon in the process. What is the frequency of the photon being emitted? (a) 1.09 10 15 Hz (b) 2.44 10 6 Hz (c) 7.31 10 14 Hz (d) 1.05 10 17 Hz (e) 2.56 10 15 Hz 26. The electron on a hydrogen atom has gained enough energy to be in the n=5 energy level. Over time the electron releases that energy, by sequentially moving the each of the lower energy levels, releasing a photon of light with each energy level change. During which of those transitions does the emitted photon have the lowest frequency? (a) From n = 5 to n = 4. (b) From n = 4 to n = 3. (c) From n = 3 to n = 2. (d) From n = 2 to n = 1. 7 of 9
(e) The photons all have the same energy. 27. An atom of He + has its electron in the n = 3 energy level. The atom is struck by a photon with an energy of 7.27 10 19 J, exciting the electron to a higher energy level. What level has the electron been excited to? (a) 2 (b) 4 (c) 5 (d) 6 (e) 7 28. What is the energy of a electron on a Li 2+ in an orbit with n = 5? (a) 7.85 10 19 J (b) 8.72 10 20 J (c) 1.31 10 18 J (d) 4.36 10 19 J (e) 2.18 10 18 J 29. The CERN Large Hadron collider is a 27 km long ring that is used to accelerate subatomic particles to very high velocities in order to collide them with other particles in experiments investigating the fundamentals of matter. If the collider is used to accelerate proton (1.67 10 27 kg) to 99% the speed of light (± 2.4 10 6 m/s), what is the uncertainty of the position of the proton in the 27 km loop? (a) 1.9 10 29 m (b) 1.3 10 14 m (c) 1.2 10 11 m (d) 1.1 10 16 m (e) 4.8 10 19 m 30. Which is not a valid quantum number for a ground state electron on an atom of arsenic? (a) n = 2, l = 1, ml = 0, ms = +½ (b) n = 4, l = 1, ml = 1, ms = +½ (c) n = 4, l = 3, ml = 2, ms = ½ (d) n = 3, l = 2, ml = 1, ms = ½ (e) n = 3, l = 0, ml = 0, ms = +½ 31. Which of the atomic orbitals listed below correctly identifies the type of orbital depicted in the image to the right? (a) 2s (b) 3p (c) 2d (d) 3d (e) 4f 8 of 9
32. Of the ions listed below, which is the smallest? (a) Sr 2+ (b) Rb + (c) None, they are all the same size. (d) Br (e) Se 2 33. Consider the second ionization energy for each of the atoms listed below. Which of these atoms will have the greatest second ionization energy? (a) Mg (b) Na (c) Ca (d) Ne (e) Rb 34. The orbital diagram below represents the ground state of the outermost electrons of which period four atom? (a) Chromium (b) Vanadium (c) Iron (d) Arsenic (e) Cobalt 35. On an atom of chlorine how many electrons have the quantum numbers which include l = 1 and ms = ½? (a) 8 (b) 2 (c) 1 (d) 5 (e) 9 36. Who s guidance explains why electrons remain unpaired until each suborbital is filled with a single electron first? (a) Pauli s exclusion principle. (b) de Broglie s effect. (c) Brannigan s law (d) Hund s rule. (e) Planck s principle. 9 of 9