Midtern#2 Winter2009

# Midtern#2 Winter2009 - MCGILL UNIVERSITY FACULTY OF SCIENCE...

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MCGILL UNIVERSITY FACULTY OF SCIENCE MIDTERM EXAMINATION CHEM 120 MONDAY MARCH 16, 2009 6:30PM–8:30PM VERSION NUMBER: 1 Instructions: BEFORE YOU BEGIN: Enter your student number and name on the computer scorecard provided, by filling in the appropriate circles. Check that the correct version number filled in. 1) There are 30 multiple choice questions to be answered on the COMPUTER GRADING sheet supplied. Choose the best response to each question. For numerical answers, assume that agreement to the first 2 significant figures is sufficient. Each question is worth 1 mark, and incorrect answers worth 0. There are no part marks available, and ONLY the computer scorecard is to be turned in for grading. You may keep this question sheet, which will allow you to check your results with the answer key posted to the class website after the exam. 2) You may use a simple scientific calculator to assist you, as long as it does NOT have text storage capability. You may also use a language translation dictionary to assist you. NO other materials are permitted (i.e.: this is a closed book exam). Sufficient data are supplied to complete all questions, and scrap paper is appended at the back for any rough calculations. 3) You have 2 hours to complete this exam. Good luck, and work efficiently!

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UNITS Conventional S.I. Volume mL or cm 3 = c m 3 or 10 -3 dm 3 Liter (L) = dm 3 Pressure atm = 760 torr = 1.013 × 10 5 Pa torr = 133.3 Pa Temperature ° C 0 ° C = 273.15 K PV L-atm = 1.013 × 10 5 dm 3 Pa =101.3 dm 3 kPa =101.3 J Energy 1 cal = 4.184 J (J= kg m 2 /s 2 ) 1 erg = 1 g cm 2 /s 2 = 10 -7 J Current ampere (A) = 1 C/s CONSTANTS Avogadro’s number N 6.022 x 10 23 mol -1 Boltzmann’s constant k 1.381 x 10 -23 J K -1 Faraday’s constant F 96 485 C mol -1 Values of R for various unit combinations 1.987 cal mol -1 K -1 0.08206 L atm mol -1 K -1 82.06 cm 3 atm mol -1 K -1 8.314 J mol -1 K -1 8.314 × 10 7 erg mol -1 K -1 8.314 dm 3 kPa mol -1 K -1 8.314 × 10 3 cm 3 kPa mol -1 K -1 Useful equations: Δ = 2 1 1 2 1 1 ln T T R H P P vap nRT PV = RT MPV m = 2 2 2 2 1 1 1 1 T n V P T n V P = RT MP d = hdg P = iMRT = π C=kP gas P A = χ A P A °
Δ G (non-standard conditions): Van ‘t Hoff Equation: Δ G = Δ G ° + RT ln Q 2 12 1 11 ln o K H KR T T ⎛⎞ −Δ =− ⎜⎟ ⎝⎠ Standard states for various elements under STP conditions: Hydrogen: H 2 (g) Carbon: C(s, graphite) Nitrogen: N 2 (g) Oxygen: O 2 (g) Copper: Cu(s) Sulphur: S(s) The Periodic Table of the Elements

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1. 0.2500 g of an unknown (non-electrolyte) compound is dissolved in 20.00 g benzene. The resulting solution freezes at 4.97 °C. Pure benzene freezes at 5.48 °C and has a freezing point depression constant of K f = 4.90 °C/ m . What is the molecular weight of the compound?
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## This note was uploaded on 04/20/2011 for the course CHEM 120 taught by Professor Barret during the Fall '08 term at McGill.

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Midtern#2 Winter2009 - MCGILL UNIVERSITY FACULTY OF SCIENCE...

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