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115 ExamI Sp08 - Name Section EXAM I Totai Points = 120 K...

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Unformatted text preview: Name Section EXAM I Totai Points = 120 K ' 1”"."3 f; ‘1! '7 LS TA Wednesday, 7:00 PM :4” Ci i” W j if i . { 004:) (11,..mo £461 [MM- art/3 January 30, 2008 ' i baam r: aware/atria? - Directions: 1. Each student is responsible for following directions. Read this page carefully. 2. Write your name and other requested information on this page and on the separate answer sheet. 3. CODE your name on the answer sheet using an ordinary (#2) pencil. 4. CODE your correct IO—digit identification number (PUID) on the answer sheet. THIS IS VERY IMPORTANT! 5. CODE your section number on the answer sheet. Please use all fog; digits, 0101, 0102, 0201, etc. This is also very important! 6. Put all calculations on the examination pages. DO NOT PUT ANY EXTRA MARKS ON THE COMPUTER ANSWER SHEET! 7. This exam consists of 20 multiple—choice questions worth 6 points each. Choose the % best or correct answer for each question and write it both on your exam paper M on the computer answer sheet. The computer answer sheet is the only one that will be graded! 8. This exam consists of 6 pages plus a Periodic Table. Please check to be sure that you have them all! ktl/z = 1n 2 ln(NO/Nt) = kt R 2 0.0821 L atm mor‘ ICl END OF EXAM 1) Please make sure that you have entered 20 answers on your scan sheet. 2) Make sure that you have entered your name, ID number, and lab section number (4 digits). 3) » , / Chemistry 115 [55 flan/I 3.194% :- You MUST turn the scan sheet in to your TA before leaving the exam! Chem 115 u Exam 1 w 01/30/08 1. Based on the current scientifically accepted model involving C02 and human activity, which of the following describes global warming? (a) a set of observations (b) a hypothesis (c) a theory (d) a set of experiments (e) a natural law Student Researcher weighs an amount of NaCl. The weight of the sample + container is 2.345 g. The container weighs 1.943 g. How many moles ofNaCl is this? (Give your answer to the correct number of significant figures.) (a) 6.87885 mmol (b) 6.8788 mmol (c) 6.879 mmol (d) 6.88 mmci (e) 6.9 mmol Sara Ann Dippity measures the volume of a solid 4 times and records the following results: 12.37 cm3, 12.41 cm3, 12.39 cnn3 and 12.38 cm3. Measurements of several other scientists in the lab give an average volume of 12.49 crn3. Which of the following statements represents the best analysis of the data? (a) Sara’s results have low precision and high accuracy (b) Sara’s results have high precision and high accuracy (c) Sara’s results have greater precision than accuracy ((1) Sara’s results have greater accuracy than precision What is the mass ofC in 1.25 g of C02? (a) 12.01 g (b) 4.58 g (c) 0.341 g (d) 0.273 g (e) 0.154 g How many neutrons and electrons are there in ”CT ? Neutrons electrons (a) 20 20 (b) 20 1 8 (c) 37 20 (d) 37 1 8 (e) 37 17 Chem 1 12 —- Exam 1 w 7/2/03 3 6. Hydrogen gas and oxygen gas are combined in a filel cell to produce water and electricity. If 3.0 moles of hydrogen gas and 2.0 moles of oxygen gas react, how many grams of water can you produce? (a) 18% (b) 36 g (C) 54 g (d) 72 g (e) 126 g 7. Which of the following is a molecular formula, but not an empirical formula? (3) H20 (b) H2804 (0) CH4 (d) N2H4 8. Which of the following is the proper molecular formula for iron(III)chIoride? (a) F63Cl (b) FeCi (C) F63C12 (d) FCCl3 (e) It cannot be determined 9. What is the stoichiometric coefficient that balances the oxygen in the following reaction? C8H1803(£) + 021%) '9 _H20(g) “l“ _C02(g) (a) 8 (b) 9 (c) 1 1 (d) 1 3 (e) 22 Chem 1 12 — Exam 1 — 7/2/03 4 10. The boxes below represent a chemical reaction between elements A (black) and B (white): Which of the following best represents the balanced equation for the reaction? (a) 2A+4B94AB2 (b) A2 + 2B2 9 4AB2 (c) 2A2+4Bg-92ABZ (d) A2 + 2B2 -) 2A8; 1i. How many liters of oxygen at STP are needed to fully combust 1.00 mole of methane in the following (unbalanced) reaction? CH4(g) + _02(8) 9 _H20(8) + __C02(g) (a) 2 L (b) 22.4 L (c) 44.8 L (d) 67.2 L (e) 89.6 L 12. A He—filled weather balloon holding 50.0 L of gas is released at sea level under conditions of 750. Torr and 20°C. What is the volume of the balloon when the balloon rises to 100,000 ft above the earth where the pressure is 4.40 Torr and the temperature is 15°C. (a) 3270 L (b) 8380 L (c) 8520 L (d) 8670 L (e) 12400 L Chem 1 22 — Exam I — 7/2/03 5 13. Which of the following lines on the figure below best represents the relationship between the volume of a gas and the pressure, other factors remaining 00nstant? Volume (L) Pressure (atm) 14. 3: Co undergoes positron emission (‘1) [3) to form which of the following isotopes? (a) :2 Fe (b) 3: Ni (O) 32176 (d) 33 CO 15. A heavy nucleus like Uranium-238 with a N/Z ratio around 1.5 and Z>83 tends to decay by which of the following processes? (a) electron capture (b) 0t decay (c) B decay (d) y decay (e) positron emission 16. Which of the following statements is not true? (a) The various forms of radioactive decay changes the value of Z, but not A. (b) A decay series can combine numerous decay steps and ends with a stable nuclide. (0) Nuclear stability can be related to the binding energy per nucleon. (d) The N/Z ratio correlates with the mode of decay of an unstable nuclide. l7. Carbon-14 has a half-life of 5,730 years. How much will the concentration of 14C have been reduced after 22,980 years? (a) by a factor of 2 (b) by a factor of 4 (c) by a factor of 8 (d) by a factor of 12 (e) by a factor of 16 Chem i 12 _ Exam 1 w 7/2/03 18. Madame Curie’s rock is determined to contain 150 time] of 238E] (tug = 4.5 x 109 years), and 50 urnol of 206Pb. Assume that all the 206Pb comes from the decay of 238U (therefore No a 200 June] ). Estimate the age of the rock. (a) 6.5 x 109 years (b) 4.5 x 109 years (c) 3.3 x 109 years (d) 1.9 x 109 years (e) 1.1 x I09 years 19. Which of the following has the largest penetration distance in biological tissue and is therefore used in the detection of PET? (3) Alpha particles (b) Beta particles (0) Positrons (d) Gamma rays (6) Electrons 20. What is the mass defect for a He nucleus? {Masses of atoms: 4H6 2 4.00260 amu; ln = 1.008665 amu; 1H e 1.007825 amu} (a) 000260 (b) 0.03038 (0) 0.00866 (d) 0.00084 (6) 1.986 En; imetLIF- _Fi l I _‘ + * .|_ ’4 IV... ,_ .. .-| . .4illllll Ll ‘1 Q y i , ...
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