Version A UNIVERSITY OF VICTORIA CHEMISTRY 102 Midterm Test 1 January 31, 2014 5-6 pm (60 minutes) Version A DISPLAY YOUR STUDENT ID CARD ON THE TOP OF YOUR DESK NOW Answer all multiple choice questions on the bubble sheet provided. Use a soft pencil. The scanner does not read ink. Complete the identification portion of the bubble sheet according to the example shown. (The studentвЂ™s name in the example is Bab Cabba.) Hand in only the bubble sheet at the end of the test period (60 minutes). A DATA sheet is included, unstapled, inside the cover page of this test. This test has 6 pages (not including the DATA sheet). Count the pages before you begin. The basic Sharp EL510 calculator or the Sharp EL-510 RNB are the only ones approved for use in Chemistry 102. DO NOT BEGIN UNTIL TOLD TO DO SO BY THE INVIGILATOR Chemistry 102, Mid-Term Test 1 Version A January 31, 2014 Page 2 of 6 This test consists entirely of multiple choice questions and is worth 50 marks. There are two marks per question. The answers for the 25 questions must be coded on the optical sense form (bubble sheet) using a SOFT PENCIL. The scanner does not read ink of any colour. Select the BEST response for each question below. 1. To increase the volume of a fixed amount of gas from 100 mL to 200 mL A. increase the temperature from 25.0 to 50.0 В°C at constant pressure B. increase the pressure from 1.00 to 2.00 atm at constant temperature C. reduce the temperature from 400 K to 200 K at constant pressure D. reduce the pressure from 608 mm Hg to 0.40 atm at constant temperature E. decrease the temperature from 600 K to 400 K. 2. Of the following gases, which ONE has the greatest density at standard temperature and pressure (STP)? A. CH4 B. NH3 D. H2 E. He C. Ne 3. The addition of 2.0 g He(g) at 25 C to a fixed-volume vessel of 10.0 L that already contains O2(g) at a temperature of 25 В°C and a pressure of 0.974 atm will: A. have no effect on the final gas pressure B. cause the final pressure to exceed 2 atm C. produce a 20% increase in gas pressure D. bring the final pressure to just slightly less than 1.0 atm E. cause the final pressure to exceed 4 atm 4. If 1.0 L of CO2(g) is compared to 1.0 L of H2(g), when both samples at a temperature of 25 В°C and one atmosphere pressure, then: A. The CO2 molecules are, on average, moving more slowly than the H2 molecules. B. There are more H2 molecules than there are CO2 molecules. C. The average kinetic energy of the CO2 molecules is greater than that of the H2 molecules. D. The CO2 and H2 molecules have the same average speed. E. The mass of the one litre sample of CO2 equals the mass of the one litre sample of H2. 5. Which ONE of the following assumptions is NOT used to explain the ideal gas law? A. Gas particles themselves occupy a negligible percentage of the total gas volume. B. Attractive and repulsive forces are negligible in gases. C. Collisions between gas molecules are perfectly elastic. D. At constant temperature, all gas molecules have the same kinetic energy. E. Gas molecules are in continuous random motion. Chemistry 102, Mid-Term Test 1 Version A January 31, 2014 Page 3 of 6 6. Which of the following molecules are greenhouse gases? (i) CO2 (ii) H2O A. i & iii (iii) NO2 B. i & iv (iv) Cl2 (v) H2 (vi) N2 C. i, ii & iii D. i & v E. i & vi 7. Which of the following statements about the atmosphere and atmospheric chemistry is INCORRECT? A. Acidity caused by acid rain can be neutralized by adding limestone, CaCO3(s), to lakes. B. The greenhouse effect contributes to maintaining a livable uniform temperature on the EarthвЂ™s surface. C. Photodissociation involves the removal of an electron from an atom or molecule as a result of the absorption of a photon. NO. Photodissociation is breaking bonds. D. A key reaction in the production of smog is the photodissociation of NO2(g) E. Lakes acidified by acid rain tend to have elevated concentrations of dissolved Al3+ ions, which are harmful to fish populations. 8. Which of the following statements are CORRECT? (i) SO2 is the only gas that contributes to the problem of acid rain. FALSE. NOx also important (ii) N2, O2, and H2O are not greenhouse gases. FALSE. Two are not, but one is. (iii) One human-caused atmospheric imbalance is too little ozone in the stratosphere and too much in the troposphere. TRUE (iv) O3 in the atmosphere protects the earth from infrared radiation. FALSE. Protects from uv. (v) The depletion of ozone over Antarctica is seasonal because it requires sunlight. TRUE A. i, iii, and v 9. B. ii, iii, and iv C. iii and v D. ii and iii E. ii, iii, and v Identify the ONE reaction listed below that best describes a reaction that contributes to the formation of ground-level photochemical smog. A. CaCO3(s) CaO(s) + CO2(g) B. 2 NO(g) + O2(g) 2 NO2(g) C. SO3(g) + H2O(в„“) H2SO4(aq) D. CO2(g) + H2O(в„“) H2CO3(aq) E. CaCO3(s) + 2 H+(aq) Ca2+(aq) + CO2(g) + H2O(aq) 10. A sample of O2 gas with a volume of 0.357 L was collected at 21oC. Calculate the volume in liters of the gas when it is cooled to 10oC if the gas is ideal and the pressure remains constant. A. 0.171 B. 0.290 C. 0.344 D. 0.357 E. 0.371 Chemistry 102, Mid-Term Test 1 Version A January 31, 2014 Page 4 of 6 11. A container holds a mixture of nitrogen, argon and methane gases. The partial pressures are 500 torr for nitrogen, 300 torr for argon and 200 torr for methane. What is the mole fraction for methane? A. 0.20 B. 0.33 C. 0.30 D. 0.50 E. 2.0 12. Consider the following 5 gases. If an equal mass of each gas is placed into a separate balloon, which gas sample will have the greatest volume? Assume that the balloons are all at the same temperature and pressure. A. He B. H2 C. N2 D. Ne E. O2 13. Consider three samples of gas: N2 at 350 K, H2 at 350 K and O2 at 273 K. Compare the average kinetic energies of the molecules in these three samples. Which statement is CORRECT? A. The lightest gas (H2) has the highest average kinetic energy and the other average kinetic energies decrease as molar mass increases. B. The heaviest gas (O2) has the highest average kinetic energy and the other average kinetic energies decrease with molar mass. C. O2 (273 K) and N2 (350 K) have the same average kinetic energy while H2 (300 K) has a lower average kinetic energy. NO. It makes no difference what temperature the H2 is. This statement is always false. D. N2 (350 K) and H2 (350 K) have the same average kinetic energy while O2 (273 K) has a lower average kinetic energy E. Additional pressure information is needed to compare average kinetic energies. 14. Which one of the following statements about the earthвЂ™s atmosphere is CORRECT? A. The mechanism for restoring the ozone layer over Antarctica involves the formation of polar stratospheric clouds. FALSE. The stratospheric clouds are part of the mechanism of destruction of the ozone layer, not restoring it. B. The first step in the formation of ozone in the stratosphere is a photoionization reaction. FALSE. ItвЂ™s a photodissociation. C. All wavelengths of solar radiation can initiate photoionization reactions. FALSE. Only UV radiation and radiation more energetic than UV. D. The temperature of the atmosphere steadily decreases with increasing altitude. FALSE. T vs altitude varies in slope, the basis for naming different atmospheric layers. E. The вЂ�holeвЂ™ in the ozone layer over Antarctica changes in magnitude and area throughout the year. TRUE Chemistry 102, Mid-Term Test 1 Version A January 31, 2014 Page 5 of 6 15. Suppose that the mid-day concentration of SO2 in the ground-level air in a city is 0.080 ppm by volume. Calculate the number of moles of SO2 in 1.0 L of this air at STP (i.e. at 0 В°C and 1 atm). A. 2.9 x 10-10 B. 9.7 x 10-7 C. 3.6 x 10-3 D. 3.6 x 10-9 E. 9.7 x 10-1 16. In North America, what is the main human-caused source of the sulfur dioxide (SO2) that contributes to such pollution problems as acid rain? A. Burning gasoline in cars and trucks. B. Mining of sulfur. C. Volcanic gases and forest fires. D. Burning coal and heavy oil for electricity, heating, and industry. See Custom Text page 284. Paragraph 3 E. Decomposition of atmospheric sulfur trioxide (SO3). 17. Which of the following statements is NOT CORRECT? A. Visible and ultraviolet radiation wavelengths reach the earthвЂ™s surface and this energy is re-emitted by the earth as infra-red radiation (heat). TRUE B. Absorption of infra-red radiation increases vibrational energy in a molecule. TRUE C. NO2 in the atmosphere is a significant contributor to the problem of acid rain. TRUE D. CO2, CH4, and water vapour are all greenhouse gases. TRUE E. Unburned hydrocarbons in the stratosphere are a significant contributor to the problem of photochemical smog. FALSE. Smog is a troposphere problem. 18. Which of the following reactions is/are NOT a significant process in the usual set of reactions that maintain the protective stratospheric ozone layer? (i) Cl(g) + O3(g) вЂ”> ClO(g) + O2(g) (ii) O(g) + O2(g) вЂ”> O3*(g) (iii) O3(g) + hv вЂ”> O2(g) + O(g) A. (i) B. (ii) C. (iii) D. (i) and (ii) E. (ii) and (iii) 19. The kinetic energy (in kJ) of a 1400 kg automobile travelling at 20 m s-1 is? A. 2.8 Г— 105 B. 14 C. 560 D. 5.60 Г— 102 E. 280 Two of the responses are the same. This was unintentional. But theyвЂ™re incorrect anyway. 20. The watt is a measure of power (rate of energy usage) equal to 1 J s-1. If the burning of exactly 1 mole of methane (natural gas, CH4) gives off 890 kJ and if this happens in 2.5 seconds, what power (in kilowatts, kW) is generated by this reaction? (This is an explosion.) A. 356 B. 890 C. 3.56 Г— 103 D. 2225 E. 89 Chemistry 102, Mid-Term Test 1 Version A January 31, 2014 Page 6 of 6 21. Calgary Alberta is a relatively high-altitude city. On a certain winter day the atmospheric pressure there was measured to be 678 torr. Suppose the partial pressure of ground-level ozone in the Calgary traffic rush-hour that day reached a level of 1.9 x 10-4 torr. What is the ground-level ozone concentration in ppm (by volume)? A. 0.28 B. 2.8 x 10-13 C. 0.82 D. 190 E. 0.24 22. The density of an unknown gas at 100В°C and 746 torr is 1.994 g Lв€’1. What is the molecular mass (molar mass (in g/mol)) of this unknown gas? A. 1689 B. 8.3 C. 62.2 D. 124.2 E. 31.0 23. What is the main basis for the division of the earthвЂ™s atmosphere into different regions or layers? A. It is convenient to deal in round numbers such as 10 km, 50 km, etc. from the earthвЂ™s surface. B. Changes in the slope of the altitude vs temperature graph define the layer boundaries. C. Most of the air is in the Troposphere, clouds are mainly in the Stratosphere, and mesons are captured in the Mesosphere. D. Weather is in the Troposphere, ozone is in the Stratosphere, and different atomic gases define the other layers E. Going upward from the earthвЂ™s surface the pressure drops in a significant step upon crossing the boundary between each consecutive pair of layers or regions. 24. Which of the following is NOT a practical partial solution to the problem of photochemical smog? A. Decreasing our use of conventional motor vehicles. YES. We could do this. B. Using catalytic converters on our motor vehicles. YES. We do this already. C. Making artificial rain to wash the polluting gases from the air in cities. NO. ThereвЂ™s no practical way to do this. What is artificial rain anyway? D. Obtaining more of our electricity from renewable sources such as wind turbines. YES. We do some of this already. E. Using pure oxygen instead of air in some industrial furnace applications. YES. Some industries do this. Pure O2 is easy enough to obtain. (Air is about 21% O2.) 25. What is the kinetic energy (in Joules) of a silver (Ag) atom moving at a speed of 980 m s-1? (Note: One atomic mass unit (amu) = 1.66 Г— 10-27kg.) A. 5.2 Г— 104 B. 1.7 Г— 10-19 C. 8.8 Г— 10-23 END D. 5.2 Г— 10-7 E. 8.6 Г— 10-20