Chapter 13: 45. For each of the following pairs of gas properties, describe the relationship between the properties, describe a simple system that could be used to demonstrate the relationship, and explain the reason for the relationship: (a) volume and pressure when number of gas particles and temperature are constant, (b) pressure and temperature when volume and the number of gas particles are constant, (c) volume and temperature when pressure and the number of gas particles are constant, (d) the number of gas particles and pressure when volume and temperature are constant, (e) the number of gas particles and volume when pressure and temperature are constant. 56. Ethylene oxide is produced from the reaction of ethylene and oxygen at 270-290 °C and 8-20 atm. In order to prevent potentially dangerous pressure buildups, the container in which this reaction takes place has a safety valve set to release gas when the pressure reaches 25 atm. If a 15-m3 reaction vessel contains 7.8 × 103 moles of gas, at what temperature will the pressure reach 25 atm? (There are 103 L per m3.) 84. The hydrogen gas used to make ammonia can be made from small hydrocarbons such as methane in the so-called steam-reforming process, run at high temperature and pressure. a. If 3.2 atm of methane at 21 °C are introduced into a container, to what temperature must the gas be heated to increase the pressure to 12 atm? b. If 4.0 × 103 L of methane gas at 21 °C is heated and allowed to expand at a constant pressure, what will the volume become in m3 when the temperature reaches 815 °C? c. What volume of methane gas at 21 °C and 1.1 atm must be compressed to yield 1.5 × 104 L of methane gas at 12 atm and 815 °C? 90. The hydrogen gas needed to make ammonia, hydrogen chloride gas, and methanol can be obtained from small hydrocarbons such as methane or propane through the steamreforming process, conducted at 41 atm and 760-980 °C. If 2.7 × 107 L of C3H8(g) at 810 °C and 8.0 atm react in the first step of the process, shown below, what is the maximum volume in liters of CO(g) at STP that can form? C3H8 + 3H2O → 3CO + 7H2 3CO + 3H2O → 3CO2 + 3H2 103. The atmosphere of Venus contains carbon dioxide and nitrogen gases. At the planet’s surface, the temperature is about 730 K, the total atmospheric pressure is 98 atm, and the partial pressure of carbon dioxide is 94 atm. If scientists wanted to collect 10.0 moles of gas from the surface of Venus, what volume of gas should they collect? Chapter 14: Acetone, CH3COCH3, is a laboratory solvent that is also commonly used as a nail polish remover. a. Describe the submicroscopic events taking place at the surface of liquid acetone when it evaporates. b. Do all of the acetone molecules moving away from the surface of the liquid escape? If not, why not? What three criteria must be met for a molecule to escape from the surface of the liquid and move into the gas phase? c. If you spill some nail polish remover on your hand, the spot will soon feel cold. Why? d. If you spill some acetone on a lab bench, it evaporates much faster than the same amount of acetone in a test tube. Why? e. If you spill acetone on a hot plate in the laboratory, it evaporates much more quickly than the same amount of acetone spilled on the cooler lab bench. Why? 50. Butane is a gas at room temperature and pressure, but the butane found in some cigarette lighters is a liquid. How can this be? 55. Classify each of the following bonds as nonpolar covalent, polar covalent, or ionic. If a bond is polar covalent, identify the atom that has the partial negative charge and the atom that has the partial positive charge. If a bond is ionic, identify the ion that has the negative charge and the ion that has the positive charge. a. N−O d. H−I g. Se−I j. F−P b. Al−Cl e. Br−Cl h. N−Sr c. Cl−N f. Cl−S i. O−F Chapter 15: 37. Would the following combinations be expected to be soluble or insoluble? a. polar solute and nonpolar solvent b. nonpolar solute and nonpolar solvent c. ionic solute and hexane d. molecular solute with small molecules and water e. hydrocarbon solute and hexane 41. Predict whether each of the following is soluble in water or not. a. potassium hydrogen sulfate, KHSO4 (used in wine making) b. the polar molecular compound propylene glycol, CH3CH(OH)CH2OH (used in some antifreezes) c. benzene, C6H6 (use to produce many organic compounds) 56. You throw a backyard party that resembles your idea of a big Texas barbecue. The guests get more food than they could possibly eat, including a big juicy steak in the center of each plate. Describe how soap or detergent can help you clean the greasy plates you’re left with when your guests go home, referring to the interactions between particles and the corresponding changes that take place on the submicroscopic level. 62. Some of the minerals found in rocks dissolve in water as it flows over the rocks. Would these minerals dissolve more quickly a. at the bottom of a waterfall or in a still pond? Why? b. in a cold mountain stream or in the warmer water downstream? Why? c. over large rocks or over sand composed of the same material? Why? 64. Solutions are called dilute when the concentration of the solute in solution is relatively low and concentrated when the concentration is relatively high. Can a solution be both dilute and saturated? Explain your answer. Chapter 16: 34. Assume that the following reaction is a single step reaction in which a C−Br bond is broken as the C−I bond is formed. The heat of reaction is +38 kJ/mol. a. With reference to collision theory, describe the general process that takes place as this reaction moves from reactants to products. b. List the three requirements that must be met before a reaction between Iand CH3Br is likely to take place. c. Explain why an I- ion and a CH3Br molecule must collide before a reaction can take place. d. Explain why, in the process of this reaction, it is usually necessary for the new C−I bonds to form at the same time as the C−Br bonds are broken. e. Draw a rough sketch of the activated complex. (You do not need to show bond angles. Be sure to show the bond that is breaking and the bond that is being formed.) f. Explain why a collision between an I- ion and a CH3Br molecule must have a certain minimum energy (activation energy) in order to proceed to products. g. The activation energy for this reaction is 76 kJ/mol. Draw an energy diagram for this reaction, showing the relative energies of the reactants, the activated complex, and the products. Using arrows show the activation energy and heat of reaction. h. Is this reaction exothermic or endothermic? i. Explain why an I- ion and a CH3Br molecule must collide with the correct orientation if a reaction between them is going to be likely to take place. 40. If both systems described by the energy diagrams in the previous problem are at the same temperature, if the concentrations of initial reactants are equivalent for each reaction, and if the orientation requirements for each reaction are about the same, which of these reactions would you expect to have the greatest forward reaction rate? Why 44. Reversible chemical reactions lead to dynamic equilibrium states. What is dynamic about these states? Why are they called equilibrium states? 55. Predict whether each of the following reactions favor reactants, products, or neither at the temperature for which the equilibrium constant is given. a. 2COF2(g) CO2(g) + CF4(g) KP = 2 at 1000 °C b. ⅛S8(s) + O2(g) SO2(g) KP = 4.2 x 1052 at 25 °C c. C2H6(g) C2H4(g) + H2(g) KP = 1.2 x 10-18 at 25 °C Ethylene, C2H4, used to make polyethylene plastics, can be made from ethane, C2H6, one of the components of natural gas. The heat of reaction for the decomposition of ethane gas into ethylene gas and hydrogen gas is 136.94 kJ per mole of C2H4 formed, so it is endothermic. The reaction is run at high temperature, in part because at 800-900 °C, the equilibrium constant for the reaction is much higher, indicating that a higher percentage of products forms at this temperature. Explain why increased temperature drives this reversible chemical reaction in the endergonic direction and why this leads to an increase in the equilibrium constant for the reaction. C2H6(g) C2H4(g) + H2(g) 67. Acetic acid, which is used to make many important compounds, is produced from methanol and carbon monoxide (which are themselves both derived from methane in natural gas) by a process called the Monsanto process. The endothermic reaction is run over a rhodium and iodine catalyst at 175 °C and 1 atm of pressure. Predict whether each of the following changes in the equilibrium system will shift the system to more products, to more reactants, or neither. Explain each answer in two ways, (1) by applying Le Chatelier’s principle and (2) by describing the effect of the change on the forward and reverse reaction rates. CH3OH(g) + CO(g) + 207.9 kJ CH3CO2H(g) Rh/I2 175 °C 1 atm a. The concentration of CO is increased by the addition of more CO. b. The concentration of CH3OH is decreased. c. The concentration of CH3CO2H(g) is decreased by removing the acetic acid as it forms. d. The temperature is decreased from 300 °C to 175 °C. e. The Rh/I2 catalyst is added to the equilibrium system
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