Chem1b-E3-Prac

Chem1b-E3-Prac - Chapter 19 Principles of Reactivity:...

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184 Chapter 19 Principles of Reactivity: Entropy and Free Energy 1. If the reaction A + B & C has an equilibrium constant greater than one, which of the following statements is correct? a) The reaction is not spontaneous. b) The forward rate of reaction is fast. c) The backward rate of reaction is slow. d) The reaction is product favored. e) All of the above statements are correct. Answer: d 2. If a chemical reaction has a positive change in entropy, D S , then a) the disorder of the system increases. b) the reaction is exothermic. c) heat goes from the system into the surroundings. d) the Gibbs free energy is negative. e) the reaction is spontaneous. Answer: a 3. Thermodynamics can be used to determine all of the following EXCEPT a) the direction in which a reaction is spontaneous. b) the extent to which a reaction occurs. c) the rate of reaction. d) the temperature at which a reaction is spontaneous. e) the enthalpy change of a reaction. Answer: c 4. Which of the following involves a decrease in entropy? a) the sublimation of carbon dioxide b) the dissolution of NaCl in water c) the decomposition of N 2 O 4 (g) to NO 2 (g) d) the evaporation of ethanol e) the freezing of liquid water into ice Answer: e 5. Which of the following substances is likely to have the highest standard entropy in the liquid state? a) CH 2 Cl 2 b) CCl 4 c) CH 3 OH d) C 5 H 12 e) C 8 H 18 Answer: e
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185 6. A statement of the second law of thermodynamics is that a) spontaneous reactions are always exothermic. b) energy is conserved in a chemical reaction. c) the entropy of the universe is continually increasing. d) the enthalpy of reaction is the difference between product and reactant enthalpies. e) the Gibbs free energy is a function of both enthalpy and entropy. Answer: c 7. Of the following product-favored processes, which are endothermic? 1. the combustion of methane to produce water and carbon dioxide 2. the expansion of an ideal gas 3. the melting of ice at temperatures greater than 0 ° C. a) 1 only b) 2 only c) 3 only d) 1 and 2 e) 2 and 3 Answer: e 8. All of the following statements concerning entropy are true EXCEPT a) entropy is zero for elements under standard conditions. b) entropy is a state function. c) a positive change in entropy denotes a change toward greater disorder. d) entropy values are greater than or equal to zero. e) the entropy a substance in the gas phase is greater than the solid phase. Answer: a 9. All of the following processes lead to an increase in entropy EXCEPT a) increasing the temperature of a gas. b) freezing a liquid. c) evaporating a liquid. d) forming mixtures from pure substances. e) chemical reactions that increase the number of moles of gas. Answer: b 10. Which reaction is likely to have a negative change in entropy? a) 2 NH 3 N 2 (g) + 3 H 2 (g) b) CaO(s) + CO 2 (g) CaCO 3 c) NaCl(s) Na + (aq) + Cl - (aq) d) N 2 O 4 2 NO 2 e) 2 C(s) + O 2 (g) 2 CO(g) Answer: b
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186 11. Calculate the standard molar entropy change for the combustion of methane.
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This note was uploaded on 10/27/2010 for the course CHEM 337 taught by Professor Kim during the Fall '10 term at CSU Sacramento.

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Chem1b-E3-Prac - Chapter 19 Principles of Reactivity:...

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