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Chemistry 12 Exam 3 Form A Nov. 15, 2000

------------------------------------------------------------------------------------------------------- The Lewis structure of acetaminophen is given below. Use this structure to answer the next 2 questions.

1. What hybrid orbitals are used for bonding by the 2 carbon atoms labeled 1 and 2? A. Both use sp3 hybrid orbitals B. Both use sp2 hybrid orbitals C. Both use sp hybrid orbitals D. Carbon 1 uses sp3 hybridization and carbon 2 uses both sp2 and sp3 hybrid orbitals E. Carbon 1 uses sp3 hybrid orbitals and carbon 2 uses sp2 hybrid orbitals ------------------------------------------------------------------------------------------------------- 2. How many σ bonds are in acetaminophen?

A. 12 B. 16

C. 20 D. 24 E. 28

------------------------------------------------------------------------------------------------------- 3. Which one of the following molecules is expected to use dsp3 hybrid orbitals when

forming covalent bonds? A. AsCl3 B. BrCl5 C. SiCl4 D. XeF4 E. ICl3 -------------------------------------------------------------------------------------------------------

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4. Which one of the following molecules would be most polar? A. CH3Cl B. CH3F C. CH3Br D. CH3I E. CCl4 ------------------------------------------------------------------------------------------------------- 5. The experimental dipole moment of HBr is 0.79 Debye. The bond length of HBr is

known to be 0.151nm (= 1.51Å). What is the partial charge on the bromine atom? A. −1.74 × 10−20 C B. −1.74 × 10−21 C C. −1.74 × 10−19 C D. −1.60 × 10−20 C E. −1.60 × 10−19 C ------------------------------------------------------------------------------------------------------- 6. Which of the following statements about acetylene are true?

1. There are 2 π bonds and 3 σ bonds.

2. The CCH bond angle is 180° 3. The molecular orbitals on the C atom are sp2 hybrid orbitals

A. Only the first statement is true. B. Both 1 and 2 are true. C. Both 2 and 3 are true. D. Both 1 and 3 are true. E. All three statements are true.

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H C C H

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7. Phosgene, a highly toxic gas that was used as a weapon in World War I, was made by combining carbon monoxide with chlorine, Cl2.

Estimate the enthalpy change for the formation of phosgene.

C≡O 1075 kJ/mol Cl−Cl 243 kJ/mol C=O 745 kJ/mol C−Cl 330 kJ/mol

A. 25.1 kJ B. 2350 kJ C. –243 kJ D. –87 kJ E. 218 kJ ------------------------------------------------------------------------------------------------------- 8. Which of the following molecules obeys the octet rule? A. XeF2 B. SF4 C. ClF3 D.SnCl3

− E. BrF5 -------------------------------------------------------------------------------------------------------- 9. What is the root mean square speed of NO gas at 323 °C?

A. 704 m/sec B. 518 m/sec C. 70.0 m/sec D. 22.3 m/sec E. 0.704 m/sec

------------------------------------------------------------------------------------------------------- 10. The tires of a car are filled on a summer day (30 °C) to a pressure of 60 psi. Assuming

that there are no leaks and that the volume of the tires doesn’t change, the pressure inside the tires on a winter day (5 °C) is:

A. 55 psi B. 52 psi C. 47 psi D. 10 psi E. Insufficient information is given. -----------------------------------------------------------------------------------------------------

Cl Cl

O

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11. Several balloons are filled to the same volume with different gases (CO, Ne, CO2,

CH4, and He). Which of the following correctly designates the order of heights to which the balloons will ascend when let free?

A. CO > CO2 > Ne > CH4 > He B. He > Ne > CO > CO2 > CH4 C. He > CH4 > Ne > CO > CO2 D. Ne > CO > CO2 > CH4 > He E. Ne > He > CH4 > CO > CO2 ------------------------------------------------------------------------------------------------------- 12. If the partition dividing the two parts of the container shown below is removed, the

final pressure in the container will be which of the following? A. 4.5 atm B. 9.0 atm C. 3.0 atm D. 4.0 atm

E. Insufficient information. -------------------------------------------------------------------------------------------------------- 13. A 1.0 L container filled with O2 gas at 50 °C is compressed into 0.5 L and the

temperature is decreased to 25 °C. Which one of the following statements is true? A. The pressure inside the container remains the same. B. The average speed of molecules in the container increases. C. The rate of collision of molecules with the sides of the container increases. D. The average speed of the molecules in the container is reduced by a factor of 2. E. None of the above statements are true. ------------------------------------------------------------------------------------------------------- 14. How many liters of propane gas (C3H8) are required to produce 6.0 L of CO2 in a

combustion reaction at a constant pressure and temperature of 1 atm and 25 °C? A. 2.0 L B. 3.0 L C. 4.0 L D. 5.0 L E. 6.0 L -------------------------------------------------------------------------------------------------------

1 L 6 atm

He

2 L 3 atm

Ne

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15. If nitric oxide (NO) is reacted with oxygen gas to form nitrogen dioxide (NO2) gas in a sealed container, which of the following statements is/are true? Assume that the temperature is constant.

A. The pressure inside the container will decrease. B. The pressure inside the container will increase. C. The average speed of molecules in the container will decrease. D. A and C are true. E. B and C are true. ------------------------------------------------------------------------------------------------------- 16. Identify all of the structures that have a bent molecular geometry.

1. CO2 2. OF2 3. XeF2 4. NO2

− A. 1 only B. 2 only C. 3 only D. 2 and 3 E. 2 and 4 ------------------------------------------------------------------------------------------------------ 17. Cisplatin is a drug used in the treatment of cancer. Its structure is shown below.

Identify the correct electron pair and molecular geometries of cisplatin and determine whether it is polar or not.

PtClH3N

H3N Cl

••

••

Electron Pair Geometry Molecular Geometry Polar A. tetrahedral tetrahedral No B. octahedral square planar Yes C. tetrahedral square planar Yes D. octahedral tetrahedral Yes E. square planar tetrahedral No -----------------------------------------------------------------------------------------------------

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18. Determine the approximate bond angles indicated

Angle #1 Angle #2 A. 109° 109° B. 180° 120° C. 120° 90° D. 109° 120° E. 120° 109° ------------------------------------------------------------------------------------------------------- 19. Rank the following compounds in terms of increasing polarity.

F

F

F

F

FF

FF

FF

(1) (2) (3) (4) A. 1 = 3 < 2 < 4 B. 1 < 4 < 3 < 2 C. 2 < 1 = 3 < 4 D. 4 < 2 < 3 < 1 E. 1 < 2 < 4 = 3 ------------------------------------------------------------------------------------------------------ 20. The concentration of ozone in Mexico City is 0.370 ppm on a day when barometric

pressure is 650 torr. What is the partial pressure of ozone? A. 2.41×10−4 torr B. 3.70×10−7 torr C. 1.76×10−3 torr D. 241 torr E. 650 torr -----------------------------------------------------------------------------------------------------

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21. Which of the following are correct statements about the valence-shell electron-pair repulsion (VSEPR) model of bonding?

1. Electron pairs orient themselves to give the smallest angles possible. 2. Bonding electron pair geometry in all cases describes the spatial

geometry of the atoms in the molecule. 3. Only bonding electron pairs are important in the VSEPR model.

A. 1 only. B. 2 only. C. 3 only. D. 1, 2, and 3 E. None of the above.

------------------------------------------------------------------------------------------------------- 22. A real gas will behave most like an ideal gas at _______ temperatures and _______

pressures.

A. high, high B. high, low C. low, high D. low, low E. all, all

------------------------------------------------------------------------------------------------------- 23. The van der Waals equation has the following form P = nRT – n2a V-nb V2

Compared to the ideal gas equation, it provides better estimates of gas pressure because it corrects for the following effect(s):

(1) Finite volume occupied by gas molecules. (2) Attractive forces between gas molecules. (3) Relative speeds of the gas molecules. (4) Kinetic energy of gas molecules.

A. 1 only B. 2 only C. 1 and 2 D. 2 and 3 E. 1,2,3,4

---------------------------------------------------------------------------------------------------- 24. Which of the following properties do greenhouse gases have?

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(1) They absorb infrared radiation (2) They block ultraviolet radiation from the sun (3) They photodissociate to form pollutant species in the atmosphere

A. 1 only B. 2 only C. 3 only D. 1 and 2 E. 2 and 3

------------------------------------------------------------------------------------------------------- 25. Which of the following statements is/are true?

1. CF4 is more polar than CH4. 2. XeF2 has a bent molecular geometry. 3. PF5 is a polar molecule. 4. CO2 has the same molecular geometry as BeF2.

A. Only 1 and 4 are true. B. Only 2 and 3 are true. C. Only 4 is true. D. All of the statements above are true. E. None of the statements above are true.

------------------------------------------------------------------------------------------------------- 26. Which of the following statements about ozone (O3) is false? A. The molecular structure is bent. B. The oxygen-oxygen bonds are of equal length and strength. C. The oxygen-oxygen bonds are longer than the oxygen-oxygen bonds in O2(g). D. The central oxygen in ozone has trigonal planar electron pair geometry. E. Three equivalent resonance structures can be drawn for ozone. ------------------------------------------------------------------------------------------------------- 27. An important reaction in the formation of photochemical smog is the photodissociation

of NO2. NO2(g) + hν → NO(g) + O(g)

The maximum wavelength of light that can cause this reaction is 420 nm. Assuming this wavelength of light is absorbed in the reaction, what is the NO bond energy (in kJ/mole)?

A. 28.5 kJ/mole B. 168 kJ/mole

C. 285 kJ/mole D. 473 kJ/mole E. 503 kJ/mole

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28. 12.3 g of gas are collected in a 50.0 L flask at 600 K. The pressure of the gas collected is 102 torr. The gas is analyzed and found to be 6.7% H, 26.7%C, 35.5% O and 31.1% N by mass. The molecular formula for the gas is:

A. CH2NO B. CH3NO C. C2H6N2O2 D. C2H4NO3 E. C2H4N2O2

------------------------------------------------------------------------------------------------------- Chemistry 12

Exam 3, November 15, 2000 Answer Key Form A

1. E 2. C 3. E 4. B 5. A 6. B (½ for A) 7. D 8. D 9. A (½ for D) 10. A 11. C 12. D (½ for E) 13. C 14. A 15. D (½ for A, ½ for C) 16. E (½ for B) 17. B 18. D 19. A 20. A 21. (E) dropped* 22. B 23. C (½ for A, ½ B) 24. A 25. C 26. E 27. C 28. C (½ for B) *Only 27 questions count on this exam.