Multiple Choice: Select the Best Answer for Each Statement Below. (30)

CHM 101 NAME ______GAGE FALL 2005 DATE: November 21, 2005 EXAM 3

Multiple Choice: Select the best answer for each statement below. (30)

_____1. A sample has a high melting point and does not conduct electricity under any conditions. The crystal type is probably:

a. ionic b. covalent c. metallic d. molecular

_____2. The surface tension of a liquid is caused primarily by:

a. molar mass c. temperature b. atmospheric pressure d. intermolecular forces

2- _____3. The hybridization of the central atom in PCl3 is:

a. sp3 b. sp4 c. sp3d d. sp3d2

_____4. When the intermolecular forces between molecules increase, the vapor pressure of the substance at room temperature:

a. decreases b. remains the same c. increases

_____5. The intermolecular forces between particles of sulfur trioxide are:

a. dipole-dipole b. London c. ion-dipole d. H-bonding

_____6. The substance with the lowest boiling point is:

a. NaBr b. AsF3 c. C6H10(OH)2 d. SiF4

_____7. The bond angles in PHCl2 are approximately

a. 180ob. 120o c. 109od. 90o

_____8. Which of the following substances will contain pi bonds?

2- a. HCN b. NCl3 c. BF3 d. SO4

_____9. As the pressure of a gas increases the:

a. temperature decreases c. volume increases b. number of moles increases d. collisions increase

1 _____10. A bond dipole will always result in a:

a. polar molecule c. molecular dipole b. polar bond d. non-polar molecule

1. You have a sample of oxygen with a volume of 485 mL at 850 mmHg and 35oC. If the volume is 650 mL at 700 mmHg, what is the temperature? (12)

2. A 50.0 g sample of water is cooled from 65oC to -30oC. o sp.htice = 2.09 J/g C vap = 2.26 kJ/g o sp.htsteam = 2.10 J/g C fus = 0.332 kJ/g o sp.htliq water = 4.18 J/g C

a. Is the overall change endothermic or exothermic? Explain. (2)

b. Explain what is happening on a molecular level at each step in the process. Include types of motions. (8)

c. Determine the amount of energy exchanged by the system. (12)

2 o 3. a. You expect the bond angles in PCl3 to be 109.5 but when measured they are 107.5o. Explain why. (4)

b. Water has a high heat of vaporization. Explain why and explain one advantage of this fact. (4)

c. You have three lab bottles and the labels have fallen off. One bottle contains a crystalline solid, the second contains a waxy substance, and the third is a liquid. The labels indicate that the substances are: C6C5CH3, NaHCO3, and C10H20.

Match the substances with the descriptions and justify your selection based on chemical properties. (4)

d. Explain what happens on a microscopic and macroscopic level when the temperature of a gas in a flexible container is raised and why. (4)

3 4. What is the pressure of 57 g of laughing gas (dinitrogen oxide) in a 4.30 x 104 L container at 66oC? (10)

5. Determine the molecular geometry for each of the following molecules. (10) Indicate which ones will show resonance.

Substance Molecular Geometry (name only) Resonance?

CH2ClBr

2- PCl3

ammonia

carbon disulfide