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Chemistry The Central Science 12th edition Theodore Brown, Eugene LeMay, Bruce Bursten, Catherine Murphy, Patrick Woodward - Solutions

A reaction for converting ketones to lactones, called the Baeyer-Villiger reaction,is used in the manufacture of plastics and pharmaceuticals. 3- Chloroperbenzoic acid is shock-sensitive, however, and prone to explode. Also, 3-chlorobenzoic acid is a waste product. An alternative process being
Distinguish among salt water, freshwater, and groundwater.
The reaction shown here was performed with an iridium catalyst, both in supercritical CO2 (scCO2) and in the chlorinated solvent CH2Cl2. The kinetic data for the reaction in both solvents are plotted in the graph. Why is this a good example of a green chemical reaction?
Which choice is greener in a chemical process? Explain. (a) Benzene as a solvent or water as a solvent. (b) The reaction temperature is 500 K, or 1000 K. (c) Sodium chloride as a by-product or chloroform (CHCl3) as a by-product.
Which choice is greener in a chemical process? Explain. (a) A reaction that can be run at 350 K for 12 hours without a catalyst or one that can be run at 300 K for 1 hour with a catalyst. (b) A reagent for the reaction that can be obtained from corn husks or one that can be obtained from
A friend of yours has seen each of the following items in newspaper articles and would like an explanation: (a) Acid rain, (b) Greenhouse gas, (c) Photochemical smog, (d) Ozone depletion. Give a brief explanation of each term and identify one or two of the chemicals associated with each.
Suppose that on another planet the atmosphere consists of 17% Kr, 38% CH4, and 45% O2. What is the average molar mass at the surface? What is the average molar mass at an altitude at which all the O2 is photodissociated?
If an average O3 molecule "lives" only 100-200 seconds in the stratosphere before undergoing dissociation, how can O3 offer any protection from ultraviolet radiation?
Show how Equations 18.7 and 18.9 can be added to give Equation 18.10.
What properties of CFCs make them ideal for various commercial applications but also make them a long-term problem in the stratosphere?
Halons are fluorocarbons that contain bromine, such as CBrF3. They are used extensively as foaming agents for fighting fires. Like CFCs, halons are very unreactive and ultimately can diffuse into the stratosphere.(a) Based on the data in Table 8.4, would you expect photodissociation of Br atoms to
It is estimated that the lifetime for HFCs in the stratosphere is 2-7 years. If HFCs have such long lifetimes, why are they being used to replace CFCs?
How does carbon dioxide interact with the world ocean?
The hydroxyl radical, OH, is formed at low altitudes via the reaction of excited oxygen atoms with water:(a) Write the Lewis structure for the hydroxyl radical. Once produced, the hydroxyl radical is very reactive. Explain why each of the following series of reactions affects the pollution in the
Explain, using Le Châtelier's principle, why the equilibrium constant for the formation of NO from N2 and O2 increases with increasing temperature, whereas the equilibrium constant for the formation of NO2 from NO and O2 decreases with increasing temperature.
Natural gas consists primarily of methane, CH4(g). (a) Write a balanced chemical equation for the complete combustion of methane to produce CO2(g) as the only carbon-containing product. (b) Write a balanced chemical equation for the incomplete combustion of methane to produce CO(g) as the only
One of the possible consequences of climate change is an increase in the temperature of ocean water. The oceans serve as a "sink" for CO2 by dissolving large amounts of it. (a) How would the solubility of CO2 in the oceans be affected by an increase in the temperature of the water? (b) Discuss the
The rate of solar energy striking Earth averages 168 watts per square meter. The rate of energy radiated from Earth's surface averages 390 watts per square meter. Comparing these numbers, one might expect that the planet would cool quickly, yet it does not. Why not?
The solar power striking Earth every day averages 168 watts per square meter. The peak electrical power usage in New York City is 12,000 megawatts. Considering that present technology for solar energy conversion is only about 10% efficient, from how many square meters of land must sunlight be
Write balanced chemical equations for each of the following reactions: (a) The nitric oxide molecule undergoes photodissociation in the upper atmosphere. (b) The nitric oxide molecule undergoes photoionization in the upper atmosphere. (c) Nitric oxide undergoes oxidation by ozone in the
(a) Explain why Mg(OH)2 precipitates when CO32- ion is added to a solution containing Mg2+. (b) Will Mg(OH)2 precipitate when 4.0 g of Na2CO3 is added to 1.00 L of a solution containing 125 ppm of Mg2+?
It has been pointed out that there may be increased amounts of NO in the troposphere as compared with the past because of massive use of nitrogen-containing compounds in fertilizers. Assuming that NO can eventually diffuse into the stratosphere, how might it affect the conditions of life on Earth?
As of the writing of this text, EPA standards limit atmospheric ozone levels in urban environments to 84 ppb. How many moles of ozone would there be in the air above Los Angeles County (area about 4000 square miles; consider a height of 10 m above the ground) if ozone was at this concentration?
The following picture represents an ion-exchange column, in which water containing "hard" ions, such as Ca2+, is added to the top of the column, and water containing "soft" ions, such as Na+, comes out the bottom. Explain what is happening in the column.
The estimated average concentration of NO2 in air in the United States in 2006 was 0.016 ppm. (a) Calculate the partial pressure of the NO2 in a sample of this air when the atmospheric pressure is 755 torr (99.1 kPa). (b) How many molecules of NO2 are present under these conditions at 20oC in a
In 1986 an electrical power plant in Taylorsville, Georgia, burned 8,376,726 tons of coal, a national record at that time. (a) Assuming that the coal was 83% carbon and 2.5% sulfur and that combustion was complete, calculate the number of tons of carbon dioxide and sulfur dioxide produced by the
The water supply for a midwestern city contains the following impurities: coarse sand, finely divided particulates, nitrate ion, trihalomethanes, dissolved phosphorus in the form of phosphates, potentially harmful bacterial strains, dissolved organic substances. Which of the following processes or
An impurity in water has an extinction coefficient of 3.45 × 103 M-1 cm-1 at 280 nm, its absorption maximum (A Closer Look, p. 564). Below 50 ppb, the impurity is not a problem for human health. Given that most spectrometers cannot detect absorbance's less than 0.0001 with good reliability, is
The concentration of H2O in the stratosphere is about 5 ppm. It undergoes photodissociation according to:(a) Write out the Lewis-dot structures for both products and reactant. (b) Using Table 8.4, calculate the wavelength required to cause this dissociation. In Table 8.4 (c) The hydroxyl radicals,
Bioremediation is the process by which bacteria repair their environment in response, for example, to an oil spill. The efficiency of bacteria for "eating" hydrocarbons depends on the amount of oxygen in the system, pH, temperature, and many other factors. In a certain oil spill, hydrocarbons from
The standard enthalpies of formation of ClO and ClO2 are 101 and 102 kJ/mol, respectively. Using these data and the thermodynamic data in Appendix C, calculate the overall enthalpy change for each step in the following catalytic cycle:What is the enthalpy change for the overall reaction that
The main reason that distillation is a costly method for purifying water is the high energy required to heat and vaporize water. (a) Using the density, specific heat, and heat of vaporization of water from Appendix B, Calculate the amount of energy required to vaporize 1.00 gal of water beginning
A reaction that contributes to the depletion of ozone in the stratosphere is the direct reaction of oxygen atoms with ozone:At 298 K the rate constant for this reaction is 4.8 Ã— 105 M-1 s-1. (a) Based on the units of the rate constant, write the likely rate law for this reaction.
Nitrogen dioxide (NO2) is the only important gaseous species in the lower atmosphere that absorbs visible light. (a) Write the Lewis structure(s) for NO2. (b) How does this structure account for the fact that NO2 dimerizes to form N2O4? Based on what you can find about this dimerization reaction in
Describe the basic goals of green chemistry.
The following data were collected for the destruction of O3 by H (O3 + H †’ O2 + OH) at very low concentrations:(a) Write the rate law for the reaction. (b) Calculate the rate constant.
The degradation of CF3CH2F (an HFC) by OH radicals in the troposphere is first order in each reactant and has a rate constant of k = 1.6 × 108 M-1 s-1 at 4oC. If the tropospheric concentrations of OH and CF3CH2F are 8.1 × 105 and 6.3 × 108 molecules/cm3, respectively, what is the rate of
The Henry's law constant for CO2 in water at 25oC is 3.1 × 10-2 M atm-1.
If the pH of a 1.0-in. rainfall over 1500 mi2 is 3.5, how many kilograms of H2SO4 are present, assuming that it is the only acid contributing to the pH?
The precipitation of Al(OH)3 (Ksp = 1.3 × 10-33) is sometimes used to purify water. (a) Estimate the pH at which precipitation of Al(OH)3 will begin if 5.0 lb of Al2(SO4)3 is added to 2000 gal of water. (b) Approximately how many pounds of CaO must be added to the water to achieve this pH?
The valuable polymer polyurethane is made by a condensation reaction of alcohols (ROH) with compounds that contain an isocyanate group (RNCO). Two reactions that can generate a urethane monomer are shown here:(i)(ii) (a) Which process, i or ii, is greener? Explain. (b) What are the hybridization
The pH of a particular raindrop is 5.6.(a) Assuming the major species in the raindrop are H2CO3(aq), HCO3-, and CO32-(aq), calculate the concentrations of these species in the raindrop, assuming the total carbonate concentration is 10 Ã— 10-5 M. The appropriate Ka values are given in
The accompanying diagram shows how the free energy, G, changes during a hypothetical reaction A(g) + B(g) †’ C(g), On the left are pure reactants, each at 1 atm, and on the right is the pure product, also at 1 atm.(a) What is the significance of the minimum in the plot?(b) What does the
Acetic acid can be manufactured by combining methanol with carbon monoxide, an example of a carbonylation reaction:(a) Calculate the equilibrium constant for the reaction at 25°C. (b) Industrially, this reaction is run at temperatures above 25°C. Will an increase in temperature produce an
The oxidation of glucose (C6H12O6) in body tissue produces CO2 and H2O. In contrast, anaerobic decomposition, which occurs during fermentation, produces ethanol (C2H5OH) and CO2.(a) Using data given in Appendix C, compare the equilibrium constants for the following reactions:(b) Compare the maximum
The conversion of natural gas, which is mostly methane, into products that contain two or more carbon atoms, such as ethane (C2H6), is a very important industrial chemical process. In principle, methane can be converted into ethane and hydrogen:In practice, this reaction is carried out in the
Cells use the hydrolysis of adenosine triphosphate (ATP) as a source of energy (Figure 19.19). The conversion of ATP to ADP has a standard free-energy change of - 30.5 kJ/mol. If all the free energy from the metabolism of glucose,goes into the conversion of ADP to ATP, how many moles of ATP can be
The potassium-ion concentration in blood plasma is about 5.0 × 10-3 M, whereas the concentration in muscle-cell fluid is much greater (0.15 M). The plasma and intracellular fluid are separated by the cell membrane, which we assume is permeable only to K+. (a) What is ΔG for the transfer of 1 mol
The relationship between the temperature of a reaction, its standard enthalpy change, and the equilibrium constant at that temperature can be expressed as the following linear equation:(a) Explain how this equation can be used to determine experimentally from the equilibrium constants at several
One way to derive Equation 19.3 depends on the observation that at constant T the number of ways, W, of arranging m ideal-gas particles in a volume V is proportional to the volume raised to the m power:Use this relationship and Boltzmann's relationship between entropy and number of arrangements
About 86% of the world's electrical energy is produced by using steam turbines, a form of heat engine. In his analysis of an ideal heat engine, Sadi Carnot concluded that the maximum possible efficiency is defined by the total work that could be done by the engine, divided by the quantity of heat
Most liquids follow Trouton's rule, which states that the molar entropy of vaporization lies in the range of 88 ± 5 J/mol-K. The normal boiling points and enthalpies of vaporization of several organic liquids are as follows:(a) Calculate for each of the liquids. Do all the liquids obey
In chemical kinetics the entropy of activation is the entropy change for the process in which the reactants reach the activated complex. The entropy of activation for bimolecular processes is usually negative. Explain this observation with reference to Figure 14.17.
Which of the following processes are spontaneous and which are nonspontaneous:(a) The ripening of a banana(b) Dissolution of sugar in a cup of hot coffee,(c) The reaction of nitrogen atoms to form N2 molecules at and 1 atm,(d) Lightning,(e) Formation of CH4 and O2 molecules from CO2 and H2O at room
The following processes were all discussed in Chapter 18, "Chemistry of the Environment." Estimate whether the entropy of the system increases or decreases during each process: (a) Photodissociation of O2(g) (b) Formation of ozone from oxygen molecules and oxygen atoms (c) Diffusion of CFCs into
Carbon disulfide (CS2) is a toxic, highly flammable substance. The following thermodynamic data are available for CS2(l) and CS2(g) at 298 K:(a) Draw the Lewis structure of the molecule. What do you predict for the bond order C-S of the bonds?(b) Use the VSEPR method to predict the structure of the
The following data compare the standard enthalpies and free energies of formation of some crystalline ionic substances and aqueous solutions of the substances: (a) Write the formation reaction for AgNO3(s). Based on this reaction, do you expect the entropy of the system to increase or decrease
Consider the following equilibrium: N2O4(g) ⇆ 2 NO2(g) Thermodynamic data on these gases are given in Appendix C. You may assume that ΔH° and ΔS° do not vary with temperature. (a) At what temperature will an equilibrium mixture contain equal amounts of the two gases? (b) At what temperature
The reaction SO2 1g2 + 2 H2S(g) ⇆ 3 S(s) + 2 H2O (g) is the basis of a suggested method for removal of SO2 from power-plant stack gases. The standard free energy of each substance is given in Appendix C. (a) What is the equilibrium constant for the reaction at 298 K? (b) In principle, is this
When most elastomeric polymers (e.g., a rubber band) are stretched, the molecules become more ordered, as illustrated here:Suppose you stretch a rubber band. (a) Do you expect the entropy of the system to increase or decrease? (b) If the rubber band were stretched isothermally, would heat need to
Which of the following processes are spontaneous:(a) The melting of ice cubes at -10°C and 1 atm pressure(b) Separating a mixture of N2 and O2 into two separate samples, one that is pure N2 and one that is pure O2(c) Alignment of iron filings in a magnetic field(d) The reaction of hydrogen gas
(a) Give two examples of endothermic processes that are spontaneous. (b) Give an example of a process that is spontaneous at one temperature but nonspontaneous at a different temperature.
Consider the vaporization of liquid water to steam at a pressure of 1 atm. (a) Is this process endothermic or exothermic? (b) In what temperature range is it a spontaneous process? (c) In what temperature range is it a nonspontaneous process? (d) At what temperature are the two phases in
The normal freezing point of n-octane (C8H18) is -57°C. (a) Is the freezing of n-octane an endothermic or exothermic process? (b) In what temperature range is the freezing of n-octane a spontaneous process? (c) In what temperature range is it a nonspontaneous process? (d) Is there any temperature
(a)What is special about a reversible process? (b) Suppose a reversible process is reversed, restoring the system to its originalstate. What can be said about the surroundings after the process is reversed? (c) Under what circumstances will the vaporization of water to steam be a reversible
(a) What is meant by calling a process irreversible? (b) After a particular irreversible process, the system is restored to its original state. What can be said about the condition of the surroundings after the system is restored to its original state? (c) Under what conditions will the
Consider a process in which an ideal gas changes from state 1 to state 2 in such a way that its temperature changes from 300 K to 200 K. (a) Describe how this change might be carried out while keeping the volume of the gas constant. (b) Describe how it might be carried out while keeping the
As shown here, one type of computer keyboard cleaner contains liquefied 1,1-difluoroethane (C2H4F2), which is a gas at atmospheric pressure. When the nozzle is squeezed, the 1, 1-difluoroethane vaporizes out of the nozzle at high pressure, blowing dust out of objects.(a) Based on your experience,
A system goes from state 1 to state 2 and back to state 1. (a) What is the relationship between the value of ΔE for going from state 1 to state 2 to that for going from state 2 back to state 1? (b) Without further information, can you conclude anything about the amount of heat transferred to the
Consider a system consisting of an ice cube. (a) Under what conditions can the ice cube melt reversibly? (b) If the ice cube melts reversibly, ΔE is zero for the process? Explain.
Consider what happens when a sample of the explosive TNT (Section 8.8: "Chemistry Put to Work: Explosives and Alfred Nobel") is detonated under atmospheric pressure. (a) Is the detonation a spontaneous process? (b) What is the sign of q for this process? (c) Can you determine whether w is positive,
(a) How can we calculate ΔS for an isothermal process? (b) Does ΔS for a process depend on the path taken from the initial state to the final state of the system? Explain.
Suppose we vaporize a mole of liquid water at 25°C and another mole of water at 100°C. (a) Assuming that the enthalpy of vaporization of water does not change much between 25°C and 100°C, which process involves the larger change in entropy? (b) Does the entropy change in either process depend
The normal boiling point of Br2(l) is 58.8°C, and its molar enthalpy of vaporization is ΔHvap = 29.6 kJ/mol. (a) When Br2(l) boils at its normal boiling point, does its entropy increase or decrease? (b) Calculate the value of ΔS when 1.00 mol of Br2(l) is vaporized at 58.8°C.
The element gallium (Ga) freezes at 29.8°C, and its molar enthalpy of fusion is ΔHfus = 5.59 kJ / mol. (a) When molten gallium solidifies to Ga(s) at its normal melting point, is ΔS positive or negative? (b) Calculate the value of when ΔS 60.0 g of Ga(l) solidifies at 29.8°C.
(a) Express the second law of thermodynamics in words. (b) If the entropy of the system increases during a reversible process, what can you say about the entropy change of the surroundings? (c) In a certain spontaneous process the system undergoes an entropy change, ΔS = 42 J/K. What can you
(a) Express the second law of thermodynamics as a mathematical equation. (b) In a particular spontaneous process the entropy of the system decreases. What can you conclude about the sign and magnitude of ΔSsurr? (c) During a certain reversible process, the surroundings undergo an entropy change,
(a) What sign for ΔS do you expect when the volume of 0.200 mol of an ideal gas at 27°C is increased isothermally from an initial volume of 10.0 L? (b) If the final volume is 18.5 L, calculate the entropy change for the process. (c) Do you need to specify the temperature to calculate the entropy
(a)What are the signs of Î”S and Î”H for the process depicted here?(b) How might temperature affect the sign of Î”G?(c) If energy can flow in and out of the system to maintain a constant temperature during the process, what can you say about the entropy change of
(a) What sign for ΔS do you expect when the pressure on 0.600 mol of an ideal gas at 350 K is increased isothermally from an initial pressure of 0.750 atm? (b) If the final pressure on the gas is 1.20 atm, calculate the entropy change for the process. (c) Do you need to specify the temperature to
For the isothermal expansion of a gas into a vacuum, ΔE = 0, q = 0, and w = 0. (a) Is this a spontaneous process? (b) Explain why no work is done by the system during this process. (c) In thermodynamics, what is the "driving force" for the expansion of the gas?
(a) What is the difference between a state and a microstate of a system? (b) As a system goes from state A to state B, its entropy decreases. What can you say about the number of microstates corresponding to each state? (c) In a particular spontaneous process, the number of microstates available to
How would each of the following changes affect the number of microstates available to a system: (a) Increase in temperature (b) Decrease in volume (c) Change of state from liquid to gas?
(a) Using the heat of vaporization in Appendix B, calculate the entropy change for the vaporization of water at 25°C and at 100°C. (b) From your knowledge of microstates and the structure of liquid water, explain the difference in these two values.
(a) What do you expect for the sign of ΔS in a chemical reaction in which two moles of gaseous reactants are converted to three moles of gaseous products? (b) For which of the processes in Exercise 19.11 does the entropy of the system increase?
(a) In a chemical reaction two gases combine to form a solid. What do you expect for the sign of ΔS? (b) How does the entropy of the system change in the processes described in Exercise 19.12?
How does the entropy of the system change when (a) A solid melts (b) A gas liquefies (c) A solid sublimes?
How does the entropy of the system change when (a) The temperature of the system increases (b) The volume of a gas increases
(a) State the third law of thermodynamics. (b) Distinguish between translational motion, vibrational motion, and rotational motion of a molecule. (c) Illustrate these three kinds of motion with sketches for the HCl molecule.
Predict the sign of Î”S accompanying this reaction. Explain your choice.
(a) If you are told that the entropy of a certain system is zero, what do you know about the system and the temperature? (b) The energy of a gas is increased by heating it. Using CO2 as an example, illustrate the different ways in which additional energy can be distributed among the molecules of
For each of the following pairs, choose the substance with the higher entropy per mole at a given temperature: (a) Ar(l) or Ar(g) (b) He(g) at 3 atm pressure or He(g) at 1.5 atm pressure, (c) 1 mol of Ne(g) in 15.0 L or 1 mol of Ne(g) in 1.50 L, (d) CO2(g) or CO2(s).
For each of the following pairs, indicate which substance possesses the larger standard entropy: (a) 1 mol of P4(g) at 300 °C, 0.01 atm, or 1 mol of As4(g) at 300°C, 0.01 atm (b) 1 mol of H2O(g) at 100°C, 1 atm, or 1 mol of H2O(l) at 100 °C, 1 atm (c) 0.5 mol of N2(g) at 298 K, 20-L volume, or
Predict the sign of the entropy change of the system for each of the following reactions: (a) N2(g) + 3 H2(g) → 2 NH3(g) (b) CaCO3(s) → CaO(s) + CO2(g) (c) 3 C2H2 (g) → C6H6 (g) (d) Al2O3(s) + 3 H2(g) → 2 Al(s) + 3 H2O(g)
Predict the sign of ΔSsys for each of the following processes: (a) Molten gold solidifies. (b) Gaseous Cl2 dissociates in the stratosphere to form gaseous Cl atoms. (c) Gaseous CO reacts with gaseous H2 to form liquid methanol, CH3OH. (d) Calcium phosphate precipitates upon mixing Ca(NO3)2(aq) and
(a) Using Figure 19.13 as a model, sketch how the entropy of water changes as it is heated from -50°C to 110°C at sea level. Show the temperatures at which there are vertical increases in entropy. (b) Which process has the larger entropy change: melting ice or boiling water? Explain.
Propanol (C3H7OH) melts at -126.5°C and boils at 97.4°C. Draw a qualitative sketch of how the entropy changes as propanol vapor at 150°C and 1 atm is cooled to solid propanol at - 150°C and 1 atm.
In each of the following pairs, which compound would you expect to have the higher standard molar entropy: (a) C2H2(g) or C2H6(g) (b) CO2(g) or CO(g)? Explain.
Cyclopropane and propylene are isomers (see Exercise 19.6) that both have the formula C3H6. Based on the molecular structures shown, which of these isomers would you expect to have the higher standard molar entropy at 25°C?
Use Appendix C to compare the standard entropies at 25°C for the following pairs of substances: (a) Sc(s) and Sc(g) (b) NH3(g) and NH3(aq) (c) 1 mol P4(g) and 2 mol P2(g) (d) C(graphite) and C(diamond). In each case explain the difference in the entropy values.

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