9. The two strands in DNA are held together by. A. dispersion forces B. dipole-dipole forces C. hydrogen bonding D. ion-dipole forces E.

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1 hemistry 400 omework 11, hapter 11 I. Multiple hoice 1. The molecules in a sample of pure liquid dichloromethane, 2 l 2, experience which of the following intermolecular forces? I. dispersion forces II. dipole-dipole forces III. hydrogen bonding (A) I only (B) II only () I and II only (D) I, II, and III 2. A beaker containing 25 ml of liquid 1-aminopentane, 3 ( 2 ) 4 N 2, is placed on a hotplate and brought to a boil. As the 1- aminopentane boils, (A) the total energy of the system stays constant. (B) the hydrogen bonding between the 1-aminopentane molecules is disrupted. () the ion-dipole forces between the 1-aminopentane molecules are disrupted. (D) pentane and ammonia gas are formed. 3. What is the principal energetic factor in the lack of miscibility between 6 14 (l) and 2 O(l)? (A) The strength of intermolecular forces of attraction between 6 14 (l) molecules (B) The strength of intermolecular forces of attraction between 2 O(l) molecules () The difference between the molecular weights of the molecules (D) The difference in electronegativity between carbon and hydrogen 4. Which compound has the highest normal boiling point? (A) 3 2 OO (B) O () 3 OO 3 (D) OO The vapor pressure of iodomethane, 3 I (M = 141.9), is 110. mm g at 266 K. A g sample of iodomethane is placed in a closed, evacuated 370. ml container at 266 K. At equilibrium, what will be the pressure in the container? (A) 96.4 mm g (B) 110. mm g () 260. mm g (D) 292. mm g 6. Which of the following substances experience London dispersion forces? I. 3 3 II. 3 O (A) I only (B) II only () Both I and II (D) Neither I nor II 7. Which of the following are ionic compounds? I. N 2 NO 2 II. N 4 NO 3 (A) I only (B) II only () Both I and II (D) Neither I nor II 8. In liquid propanol, O, which intermolecular forces are present? A. Dispersion, hydrogen bonding and dipole-dipole forces are present. B. Only dipole-dipole and ion-dipole forces are present.. Only dispersion and dipole-dipole forces are present. D. Only hydrogen bonding forces are present. 9. The two strands in DNA are held together by. A. dispersion forces B. dipole-dipole forces. hydrogen bonding D. ion-dipole forces E. Elmer's glue 1

2 10. According to the phase diagram of methanol shown below, which statement is correct? (A) Solid methanol has a greater density than liquid methanol. (B) Solid methanol sublimes at atmospheric pressure. () Solid, liquid, and gaseous methanol can only coexist at pressures above 1 atm. (D) At 200 º and 1 atm pressure, methanol is a supercritical fluid. 11. In a liquid, the energy required to increase the surface area by a unit amount is called. A. viscosity B. surface tension. capillary action D. hydrogen bonding E. Stark energy 12. Place the following substances in order of decreasing vapor pressure at a given temperature. P 5 Br 3 4 A. Br 3 > P 5 > 4 B. Br 3 > 4 > P 5. P 5 > Br 3 > 4 D. 4 > Br 3 > P 5 E. 4 > P 5 > Br 3 *13. What mass of ice at 0.0 º must be added to 100. g 2 O at 25.0 º to cool it to 0.0 º? (A) 1.25 g (B) 7.49 g () 31.3 g (D) 100. G II. Short Answer 1. Draw a picture of two atoms and use words to describe the dispersion forces between the two atoms. 2

3 2. Draw a picture of two carbon monoxide molecules and use words to describe the dipole-dipole forces between the two molecules. 3. Draw a picture of two hydrogen fluoride molecules and use words to describe the hydrogen bonding forces between the two molecules. 4. or each of the following pairs of molecules, list the dominant IM for each molecule and circle the one with the higher boiling point: A. 2 I 2 B. Nal Li. D. 5. Draw a heating curve for water with eat Added on the x-axis and Temperature on the y-axis. Label the regions according to their phases (solid, liquid, and gas) and phase transitions (solid to liquid and liquid to gas). 3

4 6. What amount of heat energy, in joules, must be removed to change 56.7 g of water vapor at 156 to liquid at 47.0? 7. The following heating curve is for 97.5 g of substance with a molar mass of 54.0 g/mol. alculate the specific heat capacity of each phase, fus, and vap. You will have to read information from the graph to answer this question. 150 Temperature ( ) 100 Temperature ( ) eat Added (kj) 4

5 8. The following data is available for the vapor pressure of nitrogen: Temperature (K) Pressure (torr) What is the heat of vaporization for nitrogen? To accomplish this, please graph the data in Excel or a similar program and use the trendline (and its equation) to determine the heat of vaporization for nitrogen. Attach your graph with the trendline. 9. Draw the setup that proves Bragg's Law, including two layers of atoms, the traveling waves of light, and the sin for the correct angle. 10. An X-ray beam with λ = 154 nm is incident on the surface of a crystal. The maximum reflection occurred at an angle of θ = Assuming n = 1, calculate the separation between layers of atoms in the crystal. 5

6 11. Draw a phase diagram for water. Label all the axes, phases, phase changes (with temperatures and pressures). Draw a horizontal line at 1 atm. or this line, draw a heating curve. Label the axes, phases, and phase transitions for the heating curve. 12. Draw a phase diagram for carbon dioxide. Label all the axes, phases, phase changes (with temperatures and pressures). Draw a horizontal line at 1 atm. or this line, draw a heating curve. Label the axes, phases, and phase transitions for the heating curve. 6

7 13. or each of the following pairs of molecules, list the dominant IM for each molecule (2 point each) and circle the one with the higher boiling point (1 point each, only awarded if your answer is correct and both dominant IMs are correct): A. B. 3 2 O N 4 l. O 2 Ne D. MgO Mgl2 E. 2 O Ne. 4 4 G. P 5 Br 3. Nal l I. J. Ne Ar K. 4 2 l 2 L. MgO MgS M. N. 2 I 2 O. Nal Li P. 7

8 14. an the acetone molecule, pictured below, hydrogen bond with another acetone molecule? Explain (your explanation can include a drawing if you want). O 15. an the acetone molecule, pictured below, hydrogen bond with a water molecule? Explain (your explanation can include a drawing if you want). O 8

Sample Exercise 11.1 Identifying Substances That Can Form Hydrogen Bonds

Sample Exercise 11.1 Identifying Substances That Can Form Hydrogen Bonds In which of these substances is hydrogen bonding likely to play an important role in determining physical properties: methane (CH