Chemistry Everyday for Everyone
Chemistry in the Public Domain: A Plethora of Misinformation—or, Don’t Believe Everything You Read in the Newspapers!1 Sidney Toby Department of Chemistry, Rutgers, the State University of New Jersey, P.O. Box 939, Piscataway, NJ 08855 As has been recently pointed out, training students involves more than teaching them algorithmic problemsolving (1): a primary purpose in general chemistry should be to emphasize critical thinking (2). This must go beyond the classroom because students are constantly being bombarded with incomplete information in the media, especially where science is involved. Newspaper reporters tend to be politically sophisticated and well grounded in current events; unfortunately their knowledge of science often leaves a lot to be desired. The resulting errors are not always obvious, and it is important training for students to be able to find these errors and correct them. We present here examples of various kinds of chemical misinformation culled from newspapers and magazines, with appropriate questions.2 The answers to the questions are grouped at the end. The excerpts vary from the comic to the tragic; some are conceptual errors, others involve serious quantitative mistakes. Quotes and Questions
Quote No. 1 What’s wrong with the following excerpt from a newspaper article (The Star Ledger, Newark, NJ) on a leak of ammonia gas from a cold storage plant? …a leak last week filled the warehouse with potentially explosive fumes, prompting the Port Authority to close the tunnel’s New York–bound tube for four hours [so that the ammonia could be removed]. The coordinator for hazardous materials said readings of 500 parts [of ammonia] per million pose a health hazard. But the readings that night were 16,000 parts per million. “When you get that high, you get in the explosive range,” he said.
Quote No. 2 Is there anything wrong with the following excerpt from a gardening column (The New York Times)? The article was concerned with ways of reducing carbon dioxide emission. One tree can assimilate about 13 pounds [5.9 kg] of carbon dioxide per year, or enough to offset the pollution produced by driving one car for 26,000 miles [42,000 km].
Can you make a rough calculation to check this statement? Assume gasoline is octane, C8H 18, and that an average car gets 25 miles per gallon (11 km/L).
Quote No. 3 Comment on the following excerpt from a newspaper article (The Star Ledger) on a sample of diethyl ether police have seized in a drug raid. ...police cordoned off a street for about an hour, fearing an explosion. The ether, seized 10 years ago as evidence
in a drug case, was discovered about noon during a routine clearance of the vault in the courthouse basement, police said. Police said prosecutor’s detectives were cleaning the evidence vault and were planning to destroy evidence no longer needed when they realized the ether had “crystallized” and was in a highly volatile state. The county’s Hazardous Materials Unit and a State Police bomb squad were dispatched…to remove the substance.
Quote No. 4 Here are two very different points of view on laundry bleach (a dilute solution of sodium hypochlorite). An article on possible home hazards stated (The Star Ledger): “Mix bleach with vinegar and you could have an explosion on your hands.” On the other hand, an employee of a corporation that manufactures bleaching materials, while agreeing that mixing chlorine bleach with acids is dangerous, was quoted as saying that it’s “no more dangerous than mixing baking soda and vinegar, two ingredients sometimes recommended as ‘green’ alternatives to conventional cleaning agents that happen to be explosive in combination.” Which of these two viewpoints do you think is right? Quote No. 5 Comment on this report on a release of hydrogen sulfide (The Star Ledger): The pressure buildup prompted a relief valve to open, allowing hydrogen sulfide to escape into the air. Hydrogen sulfide, which is flammable and can be poisonous in high concentrations, is not hazardous in small amounts, the health official said.
Quote No. 6 Correct this excerpt from a description of aspects of Dutch agriculture (The New York Times). These millions of tons of manure, chemical fertilizers and pesticides contaminate drinking water, feed algae blooms, acidify the soil and send ammonia into the air, which contributes to acid rain. Farmers have been ordered to cut use of pesticides by 50%…
Quote No. 7 The following item appeared in a magazine article on tooth decay (Discover). Fluoride strengthens teeth by bonding with calcium, the main ingredient in enamel, to form…calcium fluoride. Calcium fluoride is a harder, denser material than calcium alone, making teeth more resistant to the bacteria that cause decay.
Can you correct this statement?
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Chemistry Everyday for Everyone Quote No. 8 Correct the following (The Star Ledger): Two workmen were asphyxiated in a tragic industrial accident when they were overcome by fumes in a large tank where welding was taking place. A detective said that “burning argon gas in the welder’s torch apparently used up all the oxygen in the tank.”
Quote No. 9 An article on New Jersey’s first coal-fired power plant to be built in 30 years stated in the headline (The Star Ledger): “100 tons of fuel to be transformed into steam and electricity every day.” In the text, however, it was reported that the 224-megawatt plant will burn about 100 tons of coal in an hour. Which of these conflicting statements is correct? Assume that coal is 90% by mass carbon and the plant is 30% efficient (it’s actually higher but we’ll ignore the steam being produced). Take the heat of formation of a mole of carbon dioxide as {393 kJ and assume the tons are metric. Quote No. 10 A dermatologist’s description of a laser used to remove tattoos was given as follows (Daily Targum, Rutgers University). Light flashed in the middle of the tube goes between two mirrors and bounces back and forth. One mirror has a hole in it so the light flashes out. There is no radiation involved, because the light is amplified.”
Is this correct?
Quote No. 11 Comment on this description of the analysis of fish extracts to measure oil pollution in the Persian Gulf (The New York Times): [hours were spent] extracting the bile from their gallbladders, where metabolites of oily compounds would be stored. After running the bile through a gas chromatographer and measuring its fluorescence at various wavelengths, she could determine whether the fish had been exposed to the spill.
Quote No. 12 Criticize this description of an explosion resulting from a leaking underground pipeline (The Star Ledger): Authorities suspect gas collected in a low-lying ravine and was ignited by a passing vehicle or possibly by a pilot light in a nearby home. The pipeline carried liquefied propane gas often called LP gas, said…the Department of Public Safely spokeswoman. Natural gas liquids turn to gas when they come in contact with air.
Quote No. 13 Letter to a column in a magazine (Parade Magazine): We hear so much about global warming these days. Would it accomplish any good if all the world’s governments required their citizens to turn on all their air conditioners in their homes and offices (on a specific day) and open all their doors and windows?
Is this a good idea?
Quote No. 14 A report on the conversion of some U.S. Postal Service vehicles from gasoline to natural gas power described the advantages subsequent to the conversion and stated (The
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Star Ledger): “The converted vehicles will be equipped with tanks enabling them to hold five gallons [19 L] of compressed natural gas which will cover their regular daily routes”. Natural gas is mostly methane and suppose this is pressurized to a reasonable maximum pressure of 2500 psi (17 MPa). Postal delivery vehicles spend a lot of time starting and stopping and we shall assume a fuel consumption of 15 mile/gallon of gasoline (6.4 km/L). Natural gas engines have an efficiency comparable with those using gasoline on a weight/weight fuel basis, so taking the density of gasoline as 0.707 g/mL how far would a full tank of compressed natural gas take us? Answers to Questions for Each Quote
Answer No. 1 Ammonia is a pungent irritant but, somewhat surprisingly, it does not burn in air under normal conditions and cylinders of it are classified as “Nonflammable Gas” by the U.S. Department of Transportation. Although the gas-phase reaction 4 NH3 + 5 O2 → 4 NO + 6 H2O is exothermic by nearly a megajoule, it is controlled by kinetics, not thermodynamics. The reaction will take place in the presence of an efficient catalyst and possibly at sufficiently high ammonia concentrations, but a flame applied to a flow of ammonia in air does not result in ignition. Since ammonia does not burn in air (it will burn in pure oxygen) it does not form “potentially explosive fumes” under ordinary conditions.
Answer No. 2 We can calculate the carbon dioxide a car emits as follows. Assume that the CO2 emission arises from the combustion of octane: 2 C8H18 + 25 O 2 → 16 CO2 + 18 H2O If an average car gets 25 miles per US gallon (11 km/L), then driving a car 26,000 miles [42,000 km] requires about 1000 gallons (3800 L) of octane and will produce about eleven tons of CO2. More than 1,600 trees would be needed to assimilate that much CO2 in one year. Moreover, from the viewpoint of a tree, CO2 is not a pollutant but a raw material needed for photosynthesis!
Answer No. 3 The presence of diethyl ether generates two hazards: the vapor is very flammable, and it can form an explosively unstable peroxide on long exposure to air. Thus the detectives were right to be alarmed because a peroxide may have been present. Although the lower aliphatic peroxides (e.g., EtOOEt) are volatile liquids at room temperature, polymeric solids may form. Ether, under ordinary conditions, is always in a “highly volatile state”. Its vapor pressure is more than half an atmosphere at room temperature. Answer No. 4 Both viewpoints are wrong. Household bleaching solution is about 5% aqueous sodium hypochlorite. Vinegar is about 5% acetic acid. Mixing them would lead to the release of hypochlorous acid: H3O + + O Cl{ → H2O + HO Cl This is a hazardous reaction because hypochlorous acid is toxic and unstable. But it is not explosive at the dilutions
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Chemistry Everyday for Everyone mentioned above. (Incidentally, explosions have been reported from the reaction of OCl{ with urea and between HOCl and NH3 ). To compare a mixture of vinegar and hypochlorite with a mixture of vinegar and baking soda is even more misleading. The baking soda mixture would give carbon dioxide, which is relatively harmless. On the other hand, hypochlorite would give HOCl, which is toxic and which decomposes into the toxic gas chlorine.
Answer No. 5 If we look in a handbook of toxic materials such as Sax and Lewis’s Hazardous Chemicals Desk Reference (Van Nostrand-Reinhold, 1987), we find that the toxic limits for H2 S are actually more stringent than for carbon monoxide. Most people are unaware that fatal H2S poisoning may occur even more rapidly than poisoning from exposure to similar concentrations of the well-known poison hydrogen cyanide. Answer No. 6 A release of ammonia in the air might have deleterious effects, but a contribution to acid rain will not be one of them. Answer No. 7 Fluoride does help reduce tooth decay, but not because it forms calcium fluoride. What happens is that the fluoride ion replaces the hydroxide ion (which has a similar radius) in tooth enamel, changing hydroxyapatite, Ca5(PO4)3OH, to fluorapatite, Ca 5 (PO4 )3 F. Under acid conditions in the mouth the fluorapatite in the enamel is less soluble than hydroxyapatite; hence less decay. Actually, the most abundant element in tooth enamel is not calcium but oxygen. Answer No. 8 It is astonishing to read about “burning argon” and saddening to contemplate that anyone was allowed to use a welder’s torch in a closed container without breathing tubes. Answer No. 9 Let x be the number of hours needed to burn 100 tons (108 g) of coal. Then 8
90 g C 10 g coal × 1h × × 1 mol × 393 kJ × 30% = 224 × 106 W xh 3600s 100 g coal 12 g C mol 100%
Answer No. 11 Let us hope that the bile was passed through a gas chromatograph and not through the chromatographer! Answer No. 12 There is confusion here between natural gas and LP gas. Natural gas is mostly methane and cannot be liquefied near room temperature at any pressure (the critical temperature of methane is approximately { 80 °C). Propane, on the other hand, has a vapor pressure of only about 7 atm at room temperature. It will evaporate when the pressure drops, not necessarily when it comes in contact with air. Answer No. 13 This proposed violation of the second law of thermodynamics keeps recurring. A former mentor (Schiff, H. I., private communication) told me that 45 years ago, he asked a thermodynamics class at McGill University, Montreal, whether opening the door of a refrigerator would make the room warmer or colder. One student said it would make the room colder, and when the lecturer patiently explained that it would make the room warmer the student strongly disagreed: “No it wouldn’t. I live in an apartment building which has a single compressor unit in the basement. It would make the room colder”. The student was, of course, correct. Answer No. 14 The tank of natural gas (taken as 100% methane) pressurized to 2500 psi (17 MPa) will contain only 2.1 kg of methane at ambient temperature. Assuming the fuel consumption (by mass) is the same for a natural gas engine as for a gasoline engine, this much methane will allow the vehicle to cover only 12 miles (19 km). Clearly, one tank will not be sufficient for a day’s delivery. Conclusion As Will Rogers is reported to have said, “It’s not what you don’t know that hurts you, it’s what you know that ain’t so.” Acknowledgment I thank James J. Elliot of the Center for Advanced Food Technology, Rutgers University, for providing some of the examples quoted here.
Recalling that 1 W = 1 J/s and 1 kJ = 1000 J gives x = 1.1 hours. Thus the statement that 100 tons of coal is burned in an hour is correct.
Note
Answer No. 10 There certainly is radiation involved and the emission from a medium-power laser at any wavelength must be treated with caution. To be fair to the dermatologist, the word “radiation” to most people suggests radioactivity, not electromagnetic radiation.
Literature Cited
1. Presented at the 14th International Conference on Chemical Education, Brisbane, July 1996. 2. Some of the excerpts discussed have been given as questions in Reaction Times , the ACS student newspaper.
1. Phelps, A. J. J. Chem. Educ. 1996, 73, 301. 2. Kogut, L. S. J. Chem. Educ. 1996, 73, 218.
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