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Unformatted text preview: CHM-102
• Exam I I
Form B Summer 2010 Key Raw Score
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outside DO-236. 1. Iron metal crystallizes with a body-centered-cubic unit cell. The unit cell edge length is
323 pm. What is the radius (in pm) of an iron atom?
a. 114 pm 2. b. 162 pm c. 140 pm d. 746 pm Based on the graph given below, what is the approximate boiling point of ethanol at 0.45
atm pressure? a. 80 °C b. 20 °C c. 40 °C d. 60 °C Page 1 of 9 3. What amount of thermal energy (Q) is given off when 10 g of water, initially at 10 oC, are
converted to ice at 0 oC?
[The specific heat of water (C) is 4.18 J/g·K and ΔHfus = 6.01 kJ/mol]
a. 3.8 x 103 J b. 1.2 x 103 J c. 6.3 x 103 J d. 421 J 4. Shown below is the heating curve for a substance. Which of the following statements is
correct? 3 1 4 2 a) The segment 1 – 2 corresponds to ΔHfusion
b) The segment 2 – 3 corresponds to the specific heat of the substance as a liquid.
c) The segment 3 – 4 corresponds to ΔHvaporization
d) All of the statements are correct.
5. Imagine that you have a stoppered 125 mL Erlenmeyer flask that
contains 20 mL of water at 25 ºC. In which of the flasks pictured
below is the vapor pressure of water the same as in the original
flask? a. i and iii only b. iii only c. i only d. i, ii, and iii
Page 2 of 9 The phase diagram shown below is used to answer questions 6 and 7. 6. The point marked by the arrow “z” in the phase diagram is the
a. triple point
c. normal melting point b. critical point
d. normal boiling point 7. The region “y” corresponds to the:
a. Solid phase
b. Critical point c. Liquid phase d. Gas phase 8. Some ionic compounds crystallize in what is called the fluorite
structure. In this structure, the cations (X) form a facecentered-cubic (fcc) array and the anions (Y) occupy the eight
tetrahedral holes inside the fcc array. What is the general
formula for an ionic compound that crystallizes using the
9. d. X7Y4 b. X2Y _________ solids consist of atoms or molecules held together by dipole-dipole forces,
London disperson forces, and/or hydrogen bonds. a. Ionic b. Covalent-network c. Metallic d. Molecular 10. Which of the following liquids is immiscible with water? a.
a. Methanol b. acetone c. hexane d. acetonitrile Page 3 of 9 11. The Henry’s law constant for N2(g) at 25 °C is 6.40 x 10-4 M atm-1. What mass (in g) of N2(g)
will dissolve in 1000 mL of aqueous solution if the pressure of N2 gas is 0.800 atm?
a. 2.05 x 10-3 g b. 5.12 x 10-4 g c. 5.12 x 10-3 g d. 1.43 x 10-2 g 12. Determine the molarity of a solution prepared by dissolving 5.5 g of HCl in 200 g of C2H6O
if the density of the resulting solution is 0.79 g/mL.
a. 21 M b. 0.93 M c. 0.58 M d. 1.72 M 13. What is the mole fraction of urea (MW = 60) in a solution prepared by dissolving 16 g of
urea in 39 g of water (MW = 18) assuming the density of the resulting solution is 1.2 g/mL?
a. 0.58 b. 0.37 c. 0.13 d. 0.11 14. Which one of the following solutions will have the highest boiling point?
a. 0.25 m C6H12O6 (glucose)
c. 0.75 m CH3OH b. 0.10 m Na3PO4
d. 0.40 m CaCl2 15. An aqueous solution of KCl boils at 102 oC. What is the freezing point of this solution?
(Kb for water = 0.512 ºC/m; Kf for water = 1.86 ºC/m)
a. -7.3 oC b. -2.0 oC c. -3.6 oC d. -14 oC Page 4 of 9 16. Which of the reactions below is consistent with the following concentration profiles for
reactant and products? a. 2 NO3(g) 2 NO2(g) + O2(g) b. 2 H2O2(l) 2 H2O(l) + O2(g) c. 2 N2O5(g) 4 NO2(g) + O2(g) d. 2 NaClO3(s) 2 NaCl(s) + 3 O2(g) 17. The following experimental data were collected for the reaction
0.30 Initial rate
1.2 x 10-2
2.6 x 10-2
3.6 x 10-2
1.2 x 10-2 What is the rate law for the reaction?
a. rate = k [A]2[B]3
c. rate = k [A][B] b. rate = k [A][B]2
d. rate = k [A] Page 5 of 9 Use the following data for a first-order reaction to answer questions 18 to 20.
Time (s) Reactant (M) 2 4.24 4 3.00 6 2.12 8 1.50 10 1.06 12 0.75 18. What is the average reaction rate between 6 and 10s?
a. 1.06 Ms-1 b. 0.265 Ms-1 c. 3.77 Ms-1 d. 0.530 Ms-1 c. 1.81 s d. 6.00 s c. 5.77 s d. 0.173 s-1 19. What is the half-time (t1/2) for the reaction?
a. 4.00 s b. 8.00 s 20. What is the rate constant (k) for the reaction?
a. 2.77 s b. 5.77 s-1 21. Methanol reacts with oxygen according to the following balanced equation.
2 CH3OH(aq) + 3 O2(g) 2 CO2(g) + 4 H2O(g) Increasing which of the following would be most effective in increasing the rate of the
d. the concentration of CH3OH
the partial pressure of O2
the concentration of CO2
insufficient information to answer the question Page 6 of 9 22. The following data were collected for a first-order reaction. What was the concentration of
reactant at t = 0? a. 9.0 M b. 8.0 M c. 7.0 M d. 6.0 M 23. At elevated temperatures, nitrogen dioxide decomposes to nitrogen oxide and oxygen:
NO 2 (g) → NO (g) + 1
O 2 (g)
2 The reaction is second order in NO2 with a rate constant of 0.543 M-1s-1 at 300 °C. What
would happen if the temperature were raised to 450 °C?
D. The rate constant for the reaction will increase.
The activation energy for the reaction will increase.
Nothing, because monomolecular reactions are independent of temperature.
The reaction will become endothermic. Page 7 of 9 Important Formulas and Constants PV = nRT Pa = X a PT P1V1 P2V2
n1T1 n 2 T2 r1
M PT = P1 + P2 + P3 + ... Q = ΔH vap mol Q = ΔH fusion mol PV = M2
M1 Xa = na
nT Q = CmΔT R = 0.0821 L·atm·K-1·mol-1
K = ºC + 273
1 atm = 760 mmHg = 760 torr = 101.3 kPa
For sc: 2r = a
M= moles solute
Lsolution S g = kPg
Rate = t1 / 2 = − Δ[ A]
k For fcc: 4r = a 2
m= For bcc: 4r = a 3 moles solute
kg solvent 0
PA = χ A PA ΔTb = iK b m Rate = k[ A] m [ B ] n ppm = mg solute
kg solution ppb = μg solute
kg solution ΔT f = −iK f m
ln[ A] = −kt + ln[ A]0 − Ea k = Ae RT Page 8 of 9 Scratch paper Page 9 of 9 ...
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This document was uploaded on 09/30/2010.
- Summer '09