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Unformatted text preview: Version PREVIEW Exam 3 JOHNSON (53140) 1 This print-out should have 40 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. LDE Carbon Allotropes 001 001 5.0 points Based on your knowledge of carbon al- lotropes, You can say that G f of graphite is and G rxn of diamond graphite is . 1. zero, large 2. small, negative 3. large, small 4. positive, positive 5. zero, negative correct 6. large, zero Explanation: The standard state of carbon is graphite; consequently, graphites standard free energy of formation is zero. Diamond is actually thermodynamically less stable than graphite; consequently, diamonds reversion to graphite is spontaneous. First Law Thermo 01 002 5.0 points What is true about the first law of thermody- namics? 1. E univ = 0 correct 2. E univ &gt; 3. E univ &lt; 4. E sys &lt; 5. E sys &gt; 6. E sys = 0 Explanation: Msci 15 0505 003 5.0 points For a reaction in which gases are neither pro- duced nor consumed, H is 1. the same as E . correct 2. less than E . 3. unrelated to E . 4. greater than E . Explanation: For a reaction at constant temperature and constant pressure, E = H- ( n ) RT . If gases are neither produced nor consumed, n will be zero, so E must equal H . Spontaneous Endo Signs alt 004 5.0 points What are the signs of S surr , S sys , and S univ , respectively, for a spontaneous en- dothermic reaction? 1.- , +, + correct 2. +,- ,- 3. +, +, + 4. Cannot be predicted with certainty from the given information 5.- , +,- Explanation: Thermo Signs 005 5.0 points When water condenses, what are the signs for q , w , and S sys , respectively? 1. +,- , + 2.- , +, + 3. +,- ,- Version PREVIEW Exam 3 JOHNSON (53140) 2 4.- , +,- correct 5. +, +,- 6. +, +, + Explanation: LDE Definitions in Thermo 011 006 5.0 points Which of the following state functions are extensive? I) Pressure (P) II) Temperature (T) III) Enthalpy (H) 1. II, III 2. None are true 3. II only 4. I only 5. I, II 6. I, III 7. III only correct 8. I, II, III Explanation: Examples of extensive state functions in- clude: mass, volume, enthalpy, entropy, inter- nal energy, free energy etc. Heat of Formation 007 5.0 points Which of O 2 (g) , O 2 ( ) , H 2 (g) , H 2 ( ) , H 2 O(g) , H 2 O( ) have a heat of formation equal to zero? 1. O 2 (g), O 2 ( ), H 2 (g), H 2 ( ) 2. O 2 (g), H 2 (g) correct 3. O 2 (g), H 2 (g), H 2 O(g) 4. All of them, but only at absolute zero 5. O 2 (g), O 2 ( ), H 2 (g), H 2 ( ), H 2 O(g), H 2 O( ) Explanation: Molecules in their native state at STP have a heat of formation of zero....
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- Spring '07