# Quiz 1

## Chemistry 142 with Grisham at University of Virginia *

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Chemistry: A Molecular Approach Value Pack (includes Study Guide for Chemis...
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CHEM 142-2/152-2 Specimen Quiz 1 February 7, 2007 INSTRUCTIONS: 1. Mark the answer sheet with a #2 pencil. 2. Print your name. 3. Write in as well as bubble in your computing ID in the indicated spaces on the side of the answer sheet. 4. There are 15 questions; each counts 5 points. There is no penalty for wrong answers. 5. You have until 09:50 to complete the quiz and turn in your answer sheet. 6. Turn in only the answer sheet. You may keep the quiz booklet. 7. Write out and sign the pledge in the box on back of your answer sheet! 8. The key to this quiz will be E-mailed to you as soon as ITC responds. Length 1 Å = 10(10 m 1 in = 2.54 cm Mass 1 kg = 2.2 lb 1 amu = 1.66(10(24 g Volume 1 L = 1 dm3 = 0.266 gal Temp 0 K = -273.15 (C Force l N = 1 kg m s(2 Pressure 1 Pa = 1 N m(2 = 1 kg m(1 s(2 1 atm = 101,325 Pa = 760 mmHg = 760 torr = 14.70 lb in(2 Electric charge 1 C = 1 A s Electric potential 1V = 1 kg m2 s(3 A(1 = 1 J C(1 Energy 1 J = 1 kg m2 s(2 = 1 V C CONSTANTS Avogadro constant N = 6.022 ( 1023 mol(1 Planck constant h = 6.626 ( 10(34 J s Boltzmann constant k = 1.381 ( 10(23 J K(1 Faraday constant F = 9.649 ( 104 C mol(1 Gas constant R = 0.08206 L atm K(1 mol(1 = 8.314 J K(1 mol(1 = 1.987 cal K(1 mol(1 Speed of light c = 2.998 ( 108 m s(1 Electron charge e = 1.602 ( 10(19 C Electron mass me = 9.109 ( 10(28 g Proton mass mp = 1.673 ( 10(24 g Neutron mass mn = 1.675 ( 10(24 g (Hfusion (ice) = 6.01 kJ mol(1 (Hvap (water) = 40.67 kJ mol(1 Specific heat of ice = 2.09 J g(1 K(1 Specific heat of water = 4.18 J g(1 K(1 Specific heat of water vapor = 1.84 J g(1 K(1 ln[A]t = (kt + ln[A]o t½ = 0.693 k EMBED Equation.3 1. On a relative basis, the WEAKER the intermolecular forces in a substance: the greater its heat of vaporization the more it deviates from ideal gas behavior the greater the vapor pressure at a given temperature the higher the melting point Answer E if none of A – D is correct. 2. What is the correct order of DECREASING boiling point (highest → lowest)? A. F2 > FCl > HF > NaF B. NaF > HF > FCl > F2 C. HF > FCl > F2 > NaF D. NaF > F2 > HF > FCl E. HF > NaF > FCl > F 2 3. The phase diagram for a substance is given below: EMBED ChemDraw.Document.6.0 A sample of this substance was prepared at 1.0 atm and 100 K. In order to sublime this substance, it is necessary to A. lower P to 0.5 atm and then increase T to 200 K. B. increase P to 1.5 atm and then increase T to 300 K. C. keep P at 1.0 atm and increase T to 300 K. D. lower P to 0.5 atm and then decrease T to 50 K. 4. An aqueous solution contains 39.0% by mass of a solute of molar mass 103.0 g mol-1. What is the molality (m) of the solution? 2.45 3.79 4.68 5.31 6.21 5. At 20 °C the vapor pressure of pure methanol (CH3OH) is 0.117 atm. If 5.61 g of a nonvolatile, nondissociating solute is dissolved in 1.00 mol pure methanol, the vapor pressure of the solution is 0.107 atm. What is the molar mass (g mol-1) of the solute? 50.1 54.4 56.1 60.0 65.6 6. An aqueous solution of ribose (M = 150.1 g mol-1), a nonvolatile, non-dissociating solute, was prepared by dissolving 10.0 g in 500 g water at 25.0 °C. What is the freezing point (°C) of the solution? [Kf (H 2O) = 1.86 °C m-1] A. 0.248 B. -0.248 C. 0.068 D. -0.068 E. -0.072 7. A cucumber is placed in concentrated solution of sodium chloride (salt). Which of the following changes occurs? Water flows from the cucumber to the salt solution. Water flows from the salt solution into the cucumber. Salt flows from the solution into the cucumber. Salt precipitates from the solution. 8. A compound dissolves in water and is thought to be ionic. If 6.15 x 10-3 moles of the compound is dissolved in water to give a solution of 50.0 mL, the osmotic pressure of the solution is 8.22 atm at 20.0 °C. what is the effective number of particles formed from each formula unit of the compound? 0.85 1.03 1.86 2.34 2.78 9. Reaction rates can increase with an increase in temperature addition of a catalyst an increase in reactant concentrations both A and B all of A, B, and C 10. On a graphical plot of reactant concentration versus time for a reaction, the average rate of a reaction over a given time interval can be determined from the slope of the tangent to the curve at the point where the rate is one half the original rate. the slope of the tangent to the curve at the point where a reactant concentration is one half its original value. the slope of the straight line connecting the reactant concentrations at the limits of the time interval. all of A, B, and C none of A, B, and C 11. Initial rate data for the reaction: H2O2 + 3I- + 2H+ → I-3 + 2H2O are given below: Expt [H2O2]/mol L-1 [I-]/mol L-1 Initial rate (mol L-1 s-1) 1 0.100 5.00 x 10-4 0.135 2 0.100 1.00 x 10-3 0.268 3 0.200 1.00 x 10-3 0.538 What is the average value of the rate constant, k? (Units implied by the data given.) 2.70 x 103 2.74 x 104 137 108 56 12. Consider the reaction: N2O4 → 2NO2. If the average rate of appearance of NO2 is given by EMBED Equation.3 , how is this related to the average rate of disappearance of N2O4? +Δ[N2O4]/Δt -Δ[N2O4]/Δt -Δ[N2O4]/2Δt -2Δ[N2O4]/Δt +Δ[N2O4]/2Δt 13. For a certain reaction, a plot of ln [A]t versus t give a straight line with a slope of -1.46 s-1 and a y-intercept of 4.30. The rate constant for this reaction is 0.68 s 1.46 s-1 -1.46 s-1 4.30 s-1 -4.30 s-1 14. What is the value of the rate constant, k (s-1), in the first order decomposition: A (g) → B (s) + C (s)? The dependence on pressure of A with time is given below: Time (s) 0.0 20.0 40.0 PA (mmHg) 1420 1004 710 0.0173 0.0250 0.0563 57.7 75.1 15. A reaction is found to have rate constants, k1 = 7.83 x 10-4 L mol-1 s-1 at 389 K and k2 = 9.76 x 10-3 L mol-1 s-1 at 574 K. The activation energy (kJ) for this reaction is: 3.05 11.0 25.3 65.4 104 Write out and sign the honor pledge on the back of your answer sheet. On my honor as a student, I have neither given nor received help on this exam.

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