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[Exam Tutorial] Chem 120 Term Test 1 2012 Questions

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CHEM 120
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FACULTY OF SCIENCE MID-TERM EXAMINATION CHEMISTRY 120 GENERAL CHEMISTRY MIDTERM 1 Examiners: Prof. B. Siwick Name:_________________________ Prof. I. Butler Dr. A. Fenster INSTRUCTIONS 1. Enter your student number and name on the computer scorecard provided by filling in the appropriate circles. Check that your scorecard has the correct version number filled in (version 1). If not, fill that in. One mark will be awarded for correctly recording your student number on the scantron card. Double check that you have done that properly! 2. This examination comprises 30 questions (16 pages including cover page and 4 blank pages), but will be marked out of 31 (see point 1 above). All questions are of equal value. 3. Transfer all answers to the scantron computer scorecard provided. 4. Only the scantron card will be collected at the end of the examination period. 5. ONLY the SHARP EL510RB calculator may be used in the Midterm. Translation dictionaries are also permitted. NO notes or texts are allowed. 6. The Examination Security Monitor Program detects pairs of students with unusually similar answer patterns on multiple-choice exams. Data generated by this program can be used as admissible evidence, either to initiate or corroborate an investigation or a charge of cheating under Section 16 of the Code of Student Conduct and Disciplinary Procedures. DATA THAT MAY BE USEFUL STP: 0°C and 1 bar 1 mol gas at STP: 22.7 L –23 k = 1.38 x 10 J/K 0 K = – 273.15 °C 2 e = 2.718 1 Pa = 1 N/m 2 g = 9.81 m/s 1 atm = 101.3 kPa = 760 Torr π = 3.14 1 bar = 100,000 Pa = 100 kPa R = 8.314 J/(mol K) 1 J = 1 kg m /s2 = 1 kPaL. = 0.08206 Latm/(molK) 1 mol = 6.02 x 10 23molecules . -1 ΔH vapO)2= 44.01 kJmol 1 cal = 4.184 J 3 Density of Water: 1 g/cm d  MP P  1 N mu 2 e  3 RT RT 3 V k 2 N A u  3RT rms M P  hdg Standard states for various elements under STP conditions: Hydrogen: H (g)2 Carbon: C(s, graphite) Nitrogen: N (2) Oxygen: O (g)Cop Cpues) SulpS(u)r: 2 Cobalt: Co(s) Chlorine: Cl 2(g) 1) Which statement regarding a sample of an ideal gas is false? A) If the pressure is doubled at constant temperature, the volume decreases by a factor of two. B) If the temperature is doubled at constant pressure, the volume decreases by a factor of two. C) If the temperature is doubled at constant volume, the pressure increases by a factor of two. D) If the volume is doubled at constant temperature, the pressure decreases by a factor of two. E) If the number of moles of gas is doubled at constant temperature and pressure, the volume increases by a factor of two. 2) Halothane is a modern anesthetic that is nonflammable and relatively safe for patients. What is the molar mass of halothane (in grams per mole) if 798 milligrams occupies 92.4 milliliters at 16.5 ºC and 790 Torr? A) 197 B) 304 C) 1.24 x 103 D) 27.4 E) 209 3) A 1.54 L vessel contains He at a temperature of 22 ºC and a pressure of 270 mmHg. A 688 mL vessel contains Ne at a temperature of 36.2 ºC and a pressure of .165 atm. Both of these gases are placed in a 2.00 L vessel at 302 K. What is the final pressure (in atm) in the 2.00 L vessel? A) 0.187 B) 0.714 C) 0.0725 D) 0.460 E) 0.335 4) A 54.6 mL sample of nitrogen gas was collected over water at 23.7 ºC and a barometric pressure of 752 mmHg. What mass of nitrogen was collected? [Vapor pressure of water at 23.7 ºC is 22 mmHg] A) 60.3 mg B) 58.7 mg C) 56.8 mg D) 61.4 mg E) 63.3 mg 5) In a sample of air at STP, the ratio of the root-mean-square velocity of O to t2at of N 2i.e. u rms)/2 (Nrms i2 equal to: A) 1.27 B) 1.00 C) 0.94 D) 0.82 E) 1.12 6) The complete combustion of octane (C H (l))8i18given by the equation: 2 C 8 (18 + 25 O (g2 → 16 CO (g) +218 H O(g) 2 How many liters of CO (g) are produced at 72.4 °C and 659 mmHg for every 2 3.785 L of octane burned? (density of C 8H18l) = 0.703 g/mL) A) 6.10 L 2 B) 8.48 x 10 L C) 6.09 x 10 3 L 3 D) 2.78 x 10 L E) 9.45 L 7) The measured Pressure of a non-ideal van der Waals gas compared to an ideal gas is: A) lower, because the gases expand B) lower, because of intermolecular attractive forces C) higher, because the molecules repel each other D) lower, because the molecules occupy space E) higher, because of intermolecular attractive forces 8) Which of the following is not a part of the kinetic-molecular theory of gases? A) A gas is composed of a large number of extremely small particles B) Individual molecules may gain or lose energy as a result of collisions, but the total energy remains constant at fixed temperature C) Gas particles are involved in constant, random straight line motion. D) Gas particles collide only with the walls of the container E) Gas particles are separated by great distance; a gas is mostly empty space. 9) A gaseous mixture consists of 50.0% O 2, 25.0% N ,2and 25.0% Cl , b2 mass. At standard temperature and pressure, the partial pressure of: A) O (2) is equal to 380 torr B) Cl (2) is less than 0.25 atm C) O 2(g) is equal to 1.6 atm D) N (2) is equal to 0.20 atm E) Cl 2g) is greater than 0.25 atm 10)Assuming ideal gas behavior, which of the following gases would have the lowest density at standard temperature and pressure? A) N 2 B) Kr C) SF 6 D) Ne E) CO 2 11)The heat of fusion for water is 6.25 kJ/mol and for ethyl alcohol is 5.67 kJ/mol. The amount of heat that would melt 30.0 grams of water would melt how many grams of ethyl alcohol (C H2OH5 ? A) 33.1 g B) 11.7 g C) 31.0 g D) 8.2 g E) 84.5 g 12)The standard enthalpy of formation fo
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