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Unformatted text preview: Chapter 10: Gases and the Atmosphere 480 95. Answer/Explanation: CF 4 has no C–Cl bonds, which in CCl 4 are readily broken when exposed to UV light. Looking at the bond enthalpies, C–Cl (327 kJ/mol) is much weaker than C–F (486 kJ/mol). In fact, the bond enthalpy of C–F is very close to the bond enthalpy of O=O (498 kJ/mol)! 96 . Answer/Explanation: CH 3 F has no C–Cl bonds, which in CH 3 Cl are readily broken when exposed to UV light. Looking at the bond enthalpies, C–Cl (327 kJ/mol) is much weaker than C–F (486 kJ/mol). In fact, the bond enthalpy of C–F is very close to the bond enthalpy of O=O (498 kJ/mol)! 97. Answer: FCCl 3 , F 2 CCl 2 , F 3 CCl Strategy and Explanation: CFCs must have at least one F and one Cl atom. They must also have four halogens (either F or Cl) attached to the C atom. The set of possible variations are: FCCl 3 , F 2 CCl 2 , F 3 CCl 98 . Answer/Explanation: CFCs are not toxic. Refrigerants used before CFCs were very dangerous. One example is NH 3 , a strong-smelling, reactive chemical. In any web browser, type the keywords “CFCs” or “refrigerants” and you will get a plethora of hits. 99. Answer/Explanation: New CFCs cannot catalyze the destruction of ozone at night, because sunlight is required to initiate the first step and create the • Cl radical. However, additional reactions recreate the • Cl, which can continue to destroy ozone even at night. 100. Answer/Explanation: Ozone is formed from the reaction of oxygen and a free radical oxygen atom as shown in this equation. • O• + O 2 O 3 Sunlight is not required for this reaction to occur. Chemistry and Pollution in the Troposphere 101 . Answer: Primary pollutants (e.g., particle pollutants, including aerosols and particulates; sulfur dioxide; nitrogen oxides; hydrocarbons) secondary pollutants (e.g., ozone). (see Section 10.12) Strategy and Explanation: Primary pollutants are substances that are introduced into the air directly from their source. • Particle pollutants: pollutants made out of particles: – aerosols: particles incorporated into water droplets. – particulates: larger solid particles • Sulfur dioxide: pollutant produced when sulfur or sulfur compounds are burned in air. • Nitrogen oxides: pollutant produced when nitrogen and oxygen react at high temperatures. • Hydrocarbons: pollutants produced from many organic sources; their identity is small hydrocarbons from CH 4 to ones with six or seven carbons. Secondary pollutants are substances produced from reactions of a primary pollutants. • Ozone: ozone in the troposphere is produced from a reaction of O 2 with O 2 in the presence of intense energy (e.g., spark, lightening, etc.) • Sulfur trioxide: SO 3 is produced from the reaction of SO 2 ....
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This note was uploaded on 04/20/2008 for the course CHE 131 taught by Professor Kerber during the Spring '08 term at SUNY Stony Brook.
- Spring '08