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Problem 53
(a) What are trihalomethanes (THMs)? (b) Draw the Lewis structures of two example THMs.
- Suppose that tests of a municipal water system reveal the presence of bromate ion, BrO3-. What are the likely origins of this ion?
Problem 54
- One of the principles of green chemistry is that it is better to use as few steps as possible in making new chemicals. In what ways does following this rule advance the goals of green chemistry? How does this principle relate to energy efficiency?
Problem 55
- Discuss how catalysts can make processes more energy efficient.
Problem 56
Problem 57a
A reaction for converting ketones to lactones, called the Baeyer–Villiger reaction,
is used in the manufacture of plastics and pharmaceu- ticals. 3-Chloroperbenzoic acid is shock-sensitive, how- ever, and prone to explode. Also, 3-chlorobenzoic acid is a waste product. An alternative process being developed uses hydrogen peroxide and a catalyst consisting of tin deposited within a solid support. The catalyst is readily recovered from the reaction mixture. (a) What would you expect to be the other product of oxidation of the ketone to lactone by hydrogen peroxide?
- In the following three instances, which choice is greener in each situation? 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.
Problem 59
Problem 60
In the following three instances, which choice is greener in a chemical process? Explain. (a) A reaction that can be run at 350 K for 12 h without a catalyst or one that can be run at 300 K for 1 h with a reusable catalyst.
- 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.
Problem 61
Problem 62
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?
Problem 63
Problem 64
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?
Problem 65
- 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. (b) Propose a mechanism by which the presence of halons in the stratosphere could lead to the depletion of stratospheric ozone.
Problem 66
Problem 67
(a) What is the difference between a CFC and an HFC?
- 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.
Problem 68
Problem 69a
Natural gas consists primarily of methane, CH4(g). (a) Write balanced chemical equation for the complete combustion of methane to produce CO2(g) as the only carbon-containing product.
Problem 69b
Natural gas consists primarily of methane, CH4(g). (b) Write a balanced chemical equation for the incomplete combustion of methane to product CO(g) as the only carbon-containg product.
Problem 71a
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) The figure below shows the solubility of CO2 in water as a function of temperature. Does CO2 behave more or less similarly to other gases in this respect?
Problem 72
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?
Problem 73
The solar power striking Earth every day averages 168 watts per square meter. The highest ever recorded electrical power usage in New York City was 13,200 MW. A record established in July of 2013. Considering that present technology for solar energy conversion is about 10% efficient, from how many square meters of land must sunlight be collected in order to provide this peak power? (For compar- ison, the total area of New York City is 830 km2.)
Problem 74a,b,c
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 stratosphere.
Problem 74d
Write balanced chemical equations for each of the following reactions: (d) Nitrogen dioxide dissolves in water to form nitric acid and nitric oxide.
- Explain why Mg(OH)2 precipitates when CO32- ion is added to a solution containing Mg2+.
Problem 75
Problem 75b
(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+?
Problem 76a
(a) The EPA threshold for acceptable levels of lead ions in water is 615 ppb. What is the molarity of an aqueous solution with a concentration of 15 ppb?
Problem 76b
(b) Concentrations of lead in the bloodstream are often quoted in units of μg/dL. Averaged over the entire country, the mean concentration of lead in the blood was measured to be 1.6 μg/dL in 2008. Express this concentration in ppb.
- 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 100 m above the ground) if ozone was at this concentration?
Problem 77
Problem 78a
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).
Problem 79a
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 plant during the year.
Problem 79b
In 1986 an electrical power plant in Taylorsville, Georgia, burned 8,376,726 tons of coal, a national record at that time. (b) If 55% of the SO2 could be removed by reaction with powdered CaO to form CaSO3, how many tons of CaSO3 would be produced?