KEY Exam4 1311 F11 v A - full-length exam with answer keys and grading method for each question. Version PDF

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full-length exam with answer keys and grading method for each question. Version A F11...

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CHEM 1311: General Chemistry 1, Fall 2011 Exam #4, December 6, 2011 Class section: Instructor

Section #

Class time

Dieckmann

001

9:00 am to 9:50 am

Dieckmann

002

10:00 am to 10:50 am

Sibert

003

11:00 am to 11:50 am

Melton

004

8:00 am to 8:50 am

EXAM TYPE: A _________________________________________________________________________________ Scantron Use In general: 1. For this exam, you are allowed to use a non-programmable and non-graphing calculator that you bring to your desk. You MAY NOT borrow another person’s calculator. You MAY NOT use your cell phone, PDA, or other non-calculator device as a calculator. 2. use #2 pencil ONLY to fill out Scantron sheet, not a pen or marker 3. when filling in bubble on the scantron, be sure to fill in bubble completely, and only one bubble for each entry; pay attention to line numbers on the scantron so that you put the answer in the correct spot 4. when you first get the exam, check to make sure you have all pages of the exam and one periodic table. You should also have one scantron sheet. If you don’t have any of these, contact us immediately. 5. we will announce periodically how much time has elapsed/are left 6. if you have a question, ask (if taking the exam at disability services, let your assistant know and they can call immediately to get an answer to your question) FILLING IN SCANTRON PERSONAL INFO: Bubble info: 1. I.D. NUMBER:

4-digit exam number (left justified)

2. NAME:

LAST NAME

3. TEST FORM:

exam type (A, B, C or D)

4. SUBJECT SCORE:

your section number: (see above for list)

Vertical lines: 1. NAME: GOOD LUCK!

“Exam 4”

space

FIRST NAME

space

MI (left justified)

CHEM 1311: Exam #4

December 6, 2011

Page 2 of 7

1. Assuming ideal behavior, select the gas with the highest rate of effusion at 298 K. A. CO2 B. H2O C. H2 D. O2 E. All have the same effusion rate __________________________________________________________________________________ 2. Which of the lines on the figure below is the best representation of the relationship between the volume of a gas and its pressure, other factors remaining constant?

A. a B. b C. c D. d E. e __________________________________________________________________________________ 3. Under which set of conditions would a gas show the greatest deviation from the ideal gas law? A. –100 °C and 2.0 atm B. 200 °C and 1.0 atm C. 100 °C and 4.0 atm D. –100 ° C and 4.0 atm E. 0 °C and 2.0 atm __________________________________________________________________________________ 4. A gas evolved during the fermentation of sugar was collected at 22.5 °C and 702 mmHg. After purification, its volume was found to be 25.0 L. How many moles of gas were collected? A. 12.5 mol B. 724 mol C. 1.05 mol D. 22.4 mol E. 0.95 mol __________________________________________________________________________________ 5. Consider separate 1 mole samples of each of the following gases at 298 K and 1 atm pressure. Which gas, assuming ideal behavior, would occupy the greatest volume? E. All would occupy the same volume. __________________________________________________________________________________ 6. In which of the following compounds will the molecules not form hydrogen bonds with each other? A. CO2

A. H

B. H2O

F

C. H2

D. O2

C.

B.

D. E. __________________________________________________________________________________ 7. Select the gas with the highest average kinetic energy per mole at 298 K. E. All have the same average kinetic energy. __________________________________________________________________________________ 8. A sample of propane has a volume of 35.3 L at 315 K and 922 torr. What is its volume at STP? A. CO2

A. 49.2 L

B. H2O

B. 37.1 L

C. H2

C. 33.6 L

D. O2

D. 25.2 L

E. 30.6 L

__________________________________________________________________________________

CHEM 1311: Exam #4

December 6, 2011

Page 3 of 7

9. Which is not a property of a gas? A. density is larger than that of a liquid B. forms homogeneous mixtures with one another C. density varies with temperature D. assumes the shape and volume of its container E. is compressible __________________________________________________________________________________ 10. Hydrogen peroxide was catalytically decomposed and 75.3 mL of oxygen gas was collected over water at 25 °C and 742 torr. What mass of oxygen was collected? (Pwater = 24 torr at 25°C)? A. 0.0993 g B. 0.0931 g C. 0.00291 g D. 0.0962 g E. 0.962 g __________________________________________________________________________________ 11. A sample of carbon dioxide gas at 125 °C and 248 torr occupies a volume of 275 L. What will the gas pressure be if the volume is increased to 321 L at 125 °C? A. 356 torr B. 359 torr C. 441 torr D. 289 torr E. 212 torr __________________________________________________________________________________ 12. A sample of a gas occupies 1.40 × 103 mL at 25.0 °C and 760. mmHg. What volume will it occupy at the same temperature and 380. mmHg? A. 2.80 x 103 mL B. 1.05 x 103 mL C. 2.10 x 103 mL D. 700. mL E. 1.40 x 103 mL __________________________________________________________________________________ 13. How many liters of chlorine gas at 25.0 °C and 0.950 atm can be produced by the reaction of 12.0 g of MnO2? MnO2(s) + 4 HCl(aq) → MnCl2(aq) + 2 H2O(l) + Cl2(g) A. 0.282 L B. 3.09 L C. 5.36 × 10-3 L D. 0.138 L E. 3.55 L __________________________________________________________________________________ 14. What is the final temperature of a gas that expands from a volume of 22.4 L at 278 K to a volume of 38.3 L at constant pressure? A. 162.6 K B. 475.3 K C. 217.3 K D. 293.9 K E. 3.09 K __________________________________________________________________________________ 15. Which of the following substances should have the highest boiling point? A. Kr B. CH4 C. N2 D. CH3Cl E. Cl2 __________________________________________________________________________________ 16. A flask with a volume of 3.16 L contains 9.33 grams of an unknown gas at 32.0 °C and 1.00 atm. What is the molar mass of the gas? A. 81.4 g mol–1 B. 144 g mol–1 C. 7.76 g mol–1 –1 –1 D. 74.0 g mol E. 66.1 g mol __________________________________________________________________________________

CHEM 1311: Exam #4

December 6, 2011

Page 4 of 7

17. Tellurium is below oxygen in group VIA and thus, not surprisingly, forms compounds with formulas similar to those of oxygen. The strongest intermolecular interactions between hydrogen telluride molecules (H2Te) arise from? [Note: Te has an electronegativity value of 2.1 and hydrogen 2.2 (Pauling electronegativity values)] A. ion-dipole interactions. B. covalent bonds. C. hydrogen bonding. D. London dispersion forces. E. dipole-dipole forces. __________________________________________________________________________________ 18. A gas mixture, with a total pressure of 300.0 torr, consists of equal masses of 10.0 g of Ne and 10.0 g or Ar. What is the partial pressure of Ar, in torr? A. 100. torr B. 150. torr C. 200. torr D. 75.0 torr E. 300. torr __________________________________________________________________________________ 19. What is the volume of NH3 produced in the following reaction when 3.0 L of N2 reacts with 4.0 L of H2? N2 (g) + 3 H2 (g) → 2 NH3 (g) A. 2.66 L B. 2.0 L C. 1.5 L D. 0.66 L E. 0.5 L __________________________________________________________________________________ 20. The boiling points of the halogens increase going from F2 to I2. What type of intermolecular forces are responsible for this trend? A. London/dispersion forces B. hydrogen bonding C. covalent bonds D. dipole-dipole E. ion-dipole attraction __________________________________________________________________________________ 21. On a relative basis, the weaker the intermolecular forces in a substance: A. the greater is its boiling point. B. the greater is its vapor pressure at a particular temperature. C. the higher is its melting point. D. the greater is its viscosity. E. the larger will be its surface tension. __________________________________________________________________________________ 22. Which of the following is the correct order of boiling points for MgBr2, H2O, CH4, He? A. He < H2O < CH4 < MgBr2 B. MgBr2 < H2O < CH4 < He C. He < CH4 < MgBr2 < H2O D. He < CH4 < H2O < MgBr2 E. CH4 < He < H2O < MgBr2 __________________________________________________________________________________ 23. The molecules in a sample of solid CO are attracted to each other by a combination of: A. London forces and H-bonding. B. H-bonding and ionic bonding. C. covalent bonding and dipole-dipole interactions. D. London forces and dipole-dipole interactions. E. none of these. __________________________________________________________________________________

CHEM 1311: Exam #4

December 6, 2011

Page 5 of 7

Questions 24 and 25 refer to the phase diagram below.

Pressure

b X

Y

760 torr

Z a Temperature 24. Consider the accompanying phase diagram. A direct change from phase X to phase Z corresponds to: A. sublimation B. vaporization C. melting D. condensation E. freezing __________________________________________________________________________________ 25. The point marked "b" corresponds to the: A. normal boiling point B. sublimation point C. critical point D. triple point E. normal melting point __________________________________________________________________________________ 26. Liquid ammonia (melting point = –78 °C, boiling point = –33.4 °C) can be used as a refrigerant and heat transfer fluid. How much energy is needed to heat 25.0 g of NH3(l) from –65.0 °C to –12.0 °C? Specific heat of NH3(l)

4.7 J g–1 K–1

Specific heat of NH3(g)

2.2 J g–1 K–1

Heat of fusion

5.64 kJ mol–1

Heat of vaporization

23.5 kJ mol–1

A. 5.5 kJ B. 6.3 kJ C. 37 kJ D. 340 kJ E. 590 kJ __________________________________________________________________________________ 27. Hydrogen gas exerts a pressure of 466 torr in a container. What is this pressure in atmospheres? A. 0.217 atm B. 0.466 atm C. 0.613 atm D. 1.63 atm E. 4.60 atm __________________________________________________________________________________

CHEM 1311: Exam #4

December 6, 2011

Page 6 of 7

28. Three separate one liter containers, labeled A, B and C below, hold the following gases. A: N2 at 298 K, 0.46 atm

B: H2 at 298 K, 1.22 atm

C: He at 298 K, 1.00 atm

If each of the three samples were pumped into a single one liter container at 298 K, what would be the final pressure of the mixture? A. 1.00 atm B. 1.46 atm C. 2.68 atm D. 1.68 atm E. 2.22 atm __________________________________________________________________________________

CHEM 1311: Exam #4

December 6, 2011

Page 7 of 7

Potentially Useful Information Rydberg Equation constant (for Hydrogen):

RH = 109,678 cm–1

Constant for Bohr model of H atom:

b = 2.18 x 10–18 J

Speed of light:

c = 2.998 x 108 m s–1

Planck’s constant:

h = 6.63 x 10–34 J s

1 J = 1 kg m2 s–2 mass (me) = 9.1093897 x 10–28 g mass = 1.673 x 10–24 g mass = 1.675 x 10–24 g

electron: proton: neutron:

1 mole = 6.022 x 1023 1 amu (u) = 1.66054 x 10–24 g 1 calorie = 4.184 J 1 Newton (N) = 1 kg m s–2 1 Pa = 1 N m–2 = 1 kg m–1 s–2 1 atm

= = = = =

760 mm Hg 760 torr 101,325 Pa 1.01325 bar 14.7 psi (pounds per sq. in)

R = 0.08206 L atm mol–1 K–1 = 8.314 J mol–1 K–1

charge (e) = –1.60 x 10–19 C...