Midt2rev_sol - 2/20/06 Midterm 2 Review: Solutions NOTE:...

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2/20/06 1 Midterm 2 Review: Solutions NOTE: These review sheets cover only selected topics from Chapters 8-13 and are not meant to be a comprehensive review. Topics included in Chapters 8-13 that are not included on these review sheets may appear on the midterm exam. Chapter 8: Chemical Energy 1) Endothermic and exothermic reactions a) Exothermic reactions give off energy. List examples of different forms of energy released by chemical exothermic reactions. Some examples seen in class: thermal energy (hot pack), visible light (glow sticks), electrical energy (batteries) b) Endothermic reactions take in energy. What are some indicators that a reaction is endothermic? Give examples. An object feels cold or its temperature decreases (cold pack) A reaction absorbs more energy than it gives off. (Green plants absorb radiant energy from the sun for photosynthesis.) A reaction requires a continuing energy input (electroplating, electrolysis of water) c) Can a reaction that requires an initial input of activation energy be exothermic? Give an example to support your answer. Yes. Lighting a candle requires an input of energy from a match or lighter. However, the reaction of burning the candle is exothermic because more energy is given off when the candle burns than is put in to light it. 2) Chemical binding energy A chemical reaction required 20 joules of energy to break the existing chemical bonds and released 45 joules of energy. The reaction was a) exothermic and took in 25 joules of energy. b) endothermic and released 25 joules of energy. c) endothermic and took in 20 joules of energy. d) exothermic and released 45 joules of energy. e) exothermic and released 25 joules of energy . Another chemical reaction required 50 joules of energy to break the existing chemical bonds, but 30 joules of energy were given off when new bonds were formed. The reaction was a) endothermic and took in 50 joules of energy. b) endothermic and released 30 joules of energy. c) exothermic and released 30 joules of energy. d) exothermic and took in 50 joules of energy. e) endothermic and took in 20 joules of energy .
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2/20/06 2 Chapter 9: Chemical Energy 3) Nuclear Reactions a) How can an atom of one element change into an atom of a different element? Protons can be added to or removed from atomic nuclei. A neutron in the nucleus can be changed into a proton, or a proton can be changed into a neutron. b) Write the equation for the nuclear reaction that occurs when a neutron emits an electron and becomes a proton. ν + + 0 0 0 1 1 1 1 0 e p n , where ν denotes an antineutrino c) Write the equation for the nuclear reaction that occurs when a proton emits an antielectron and becomes a neutron. ν
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Midt2rev_sol - 2/20/06 Midterm 2 Review: Solutions NOTE:...

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