Intermolecular Interactions Concept Review Exercise 1. What types of intermolecular interactions can exist in compounds? 2. What is the difference between covalent network and covalent molecular compounds? Answer 1. ionic bonding, network covalent, dispersion forces, dipole-dipole interactions, and hydrogen bonding. 2. Covalent network compounds contain atoms that are covalently bonded to other individual atoms in a giant 3-dimensional network. Covalent molecular compounds contain individual molecules that are attracted to one another through dispersion, dipole-dipole or hydrogen bonding. Exercises List the three common phases in the order you are likely to find them—from lowest temperature to highest temperature. List the three common phases in the order they exist from lowest energy to highest energy. List these intermolecular interactions from weakest to strongest: London forces, hydrogen bonding, and ionic interactions. List these intermolecular interactions from weakest to strongest: covalent network bonding, dipole-dipole interactions, and dispersion forces. What type of intermolecular interaction is predominate in each substance? water (H 2 O) sodium sulfate (Na 2 SO 4 ) decane (C 10 H 22 ) What type of intermolecular interaction is predominate in each substance? diamond (C, crystal) helium (He) ammonia (NH 3 ) Explain how a molecule like carbon dioxide (CO 2 ) can have polar covalent bonds but be nonpolar overall. Sulfur dioxide (SO 2 ) has a formula similar to that of carbon dioxide (see Exercise 7) but is a polar molecule overall. What can you conclude about the shape of the SO 2 molecule? What are some of the physical properties of substances that experience covalent network bonding? What are some of the physical properties of substances that experience only dispersion forces? Answers solid, liquid, and gas 2. solid, liquid, and gas London forces, hydrogen bonding, and ionic interactions 4. dispersion, dipole-dipole, network covalent hydrogen bonding ionic interactions dispersion forces 6. a. network covalent b. dispersion c. hydrogen bonding The two covalent bonds are oriented in such a way that their dipoles cancel out. 8. SO 2 is not a linear molecule. It has a bent or V-shape. 9. very hard, high melting point 10. very soft, very low melting point Solids and Liquids Concept Review Exercise How do the strengths of intermolecular interactions in solids and liquids differ? Answer Solids have stronger intermolecular interactions than liquids do. Exercises What are the general properties of solids? What are the general properties of liquids What are the general properties of gases? What phase or phases have a definite volume? What phase or phases do not have a definite volume? Name a common substance that forms a crystal in its solid state. Name a common substance that forms an amorphous solid in its solid state. Are substances with strong intermolecular interactions likely to be solids at higher or lower temperatures? Explain. Are substances with weak intermolecular interactions likely to be liquids at higher or lower temperatures? Explain. State two similarities between the solid and liquid states. State two differences between the solid and liquid states. If individual particles are moving around with respect to each other, a substance may be in either the _______ or ________ state but probably not in the _______ state. If individual particles are in contact with each other, a substance may be in either the ______ or _______ state but probably not in the ______ state. Answers hard, specific volume and shape, high density, cannot be compressed 2. fixed volume, no definite shape, high density, individual molecules touch each other but in a random way variable volume and shape, low density, compressible 4. solid and liquid have definite volume; gas has no definite volume sodium chloride (answers will vary) 6. glass At higher temperatures, their intermolecular interactions are strong enough to hold the particles in place. 8. Substances with weak intermolecular interactions are likely to be liquids at lower temperatures. Their attractive forces are more easily broken hence they melt more readily. high density; definite volume 10. Solids have definite shape while liquids don't. In solids, molecules occupy fixed positions in a pattern, while in liquids, the molecules are moving in a random arrangement. 11. liquid; gas; solid 12. solid; liquid; gas 8.3: Gases and Pressure Concept Review Exercise What is pressure, and what units do we use to express it? Answer Pressure is the force per unit area; its units can be pascals, torr, millimeters of mercury, or atmospheres. Exercises What is the kinetic theory of gases? According to the kinetic theory of gases, the individual gas particles are (always, frequently, never) moving. Why does a gas exert pressure? Why does the kinetic theory of gases allow us to presume that all gases will show similar behavior? Answers Gases are composed of tiny particles that are separated by large distances. Gas particles are constantly moving, experiencing collisions with other gas particles and the walls of their container. The velocity of gas particles is related to the temperature of a gas. Gas particles do not experience any force of attraction or repulsion with each other. 2. always A gas exerts pressure as its particles rebound off the walls of its container. 4. Because the molecules are far apart and don't have attractive forces between them 8.4: Gas Laws Concept Review Exercises What properties do the gas laws help us predict? What makes the ideal gas law different from the other gas laws? Answers Gas laws relate four properties: pressure, volume, temperature, and number of moles. The ideal gas law does not require that the properties of a gas change. Exercises A sample of nitrogen gas is confined to a balloon that has a volume of 1.88 L and a pressure of 1.334 atm. What will be the volume of the balloon if the pressure is changed to 0.662 atm? Assume that the temperature and the amount of the gas remain constant. Use the ideal gas law to show that 1 mol of a gas at STP has a volume of about 22.4 L. How many moles of gas are there in a 27.6 L sample at 298 K and a pressure of 1.44 atm? What must V be for a gas sample if n = 4.55 mol, P = 7.32 atm, and T = 285 K? Apply Henry’s Law to the diagram below to explain: a) why oxygen diffuses from the alveoli of the lungs into the blood and from the blood into the tissues of the body. b) why carbon dioxide diffuses from the tissues into the blood and from the blood into the alveoli and then finally out into the atmosphere. Answers 3.79 L The ideal gas law confirms that 22.4 L equals 1 mol. 1.63 mol 14.5 L Gases diffuse from high concentration to low concentration (Henry's Law). The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood . It's also higher partial pressure in the blood than in the tissues, hence it transfers to the tissues. On the other hand, carbon dioxide diffuses from the tissues (highest CO 2 partial pressure) and across the respiratory membrane from the blood into the alveoli and out to the atmosphere.