chem_126_2010_Common_3_xkxjdjd

chem_126_2010_Common_3_xkxjdjd - Chem 126 Common 3 Part I...

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Chem 126 Common 3 Part I April, 23, 2010 ANSWERS 1. What is the oxidation state of phosphorus in 2 4 HPO - ? (a) 1 (b) 2 (c) 3 (d) 5 (e) 7 2. Which of the following statements about entropy is false? (a) The standard entropy of formation of N 2 is zero. (b) Entropy and heat capacity have the same units. (c) The entropy decreases for the reaction 2H 2 (g) + O 2 (g) 2H 2 O(l). (d) The entropy of a sugar cube and water is smaller than the entropy of the sugar cube dissolved in the water. (e) The entropy of C 2 F 4 is smaller than the entropy of C 2 F 4 H 2 . 3. Which of the following processes is NOT ALWAYS spontaneous? (a) The voltage of the reaction is positive. (b) The change in free energy of a reaction is negative. (c) The reaction is exothermic. (d) Q for a reaction is less than the equilibrium constant. (e) At constant pressure, H rxn > 0 (endothermic), S rxn > 0 and T is very large. 4. What is w when E = -1,500 J and 2,000 J of heat are added? (a) 3,500 J (b) -3,500 J (c) 500 J (d) -500 J (e) none of the above ( 29 ( 29 ( 29 2 4 2 136 ; 235 / o rxn C s Cl g CCl g H kJ S J K + = - ∆ = - 5. Calculate o rxn G for the above reaction at 200 o C. (a) 1.11x10 5 kJ (b) -25 kJ (c) 99 kJ (d) -99 kJ (e) -371 kJ 6. Above about what temperature is the above reaction no longer spontaneous? (Pick closest.) (a) 400 K (b) 500 K (c) 600 K (d) 700 K (e) 800 K
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7. Calculate the free energy of formation for ethane, C 2 H 6 . 1,467 o rxn G kJ = - for the following reaction: C 2 H 6 (g) + 3.5O 2 (g) 2CO 2 (g) + 3H 2 O (l ) (a) None of the below (b) 836 kJmol -1 (c) -836 kJmol -1 (d) 32 kJmol -1
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This note was uploaded on 03/30/2012 for the course CHEM 126 taught by Professor Biolsi during the Spring '08 term at NJIT.

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chem_126_2010_Common_3_xkxjdjd - Chem 126 Common 3 Part I...

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