CH 302 Holcombe Hwk #1

CH 302 Holcombe Hwk #1 - perlick (app582) Homework #1...

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Unformatted text preview: perlick (app582) Homework #1 holcombe (51160) 1 This print-out should have 22 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points What factor determines whether a reaction will be exothermic or endothermic? 1. the relative concentrations of reactants and products in solution 2. the difference in energy between reactants and products correct 3. the heat properties of the products 4. the activation energy of the reaction 5. the speed of the reaction Explanation: H is the energy difference between the products and reactants; H for exothermic reactions is negative, and H for endother- mic reactions is positive. 002 10.0 points A reaction which is exothermic will be sponta- neous at (all/no) temperatures if S is (posi- tive/negative). 1. no, positive 2. no, negative 3. all, positive correct 4. all, negative Explanation: If H is negative (i.e. the reaction is exothermic) it will be spontaneous at all tem- peratures as long as S is positve. 003 10.0 points Pentane (C 5 H 12 ) is burned in oxygen to produce carbon dioxide and water. The heat of combustion of pentane is -4112 kJ/mole. The standard combustion reaction of pentane would be a chemical equation with A moles of pentane, B moles of oxygen, C moles of carbon dioxide, and D moles of water. What are the values for A, B, C, and D, respectively? 1. 2; 4; 5; 4 2. 1; 8; 5; 6 correct 3. 2; 6; 2; 6 4. 1; 4; 4; 6 5. 1; 6; 4; 6 6. 2; 4; 2; 4 7. 2; 4; 4; 4 8. 1; 6; 5; 6 Explanation: 004 10.0 points Determine the standard reaction enthalpy for the partial combustion of methane to carbon monoxide according to the following reaction: 2 CH 4 (g) + 3 O 2 (g)- 2 CO(g) + 4 H 2 O( ) The standard heat of combustion of CH 4 (g) is- 890 kJ / mol and of CO(g)- 283 kJ / mol. 1.- 1110 . 2 kJ/mol of rxn 2.- 1214 kJ / mol correct 3.- 975 . 0 kJ/mol of rxn 4.- 690 . 72 kJ/mol of rxn 5.- 1000 . 3 kJ/mol of rxn 6.- 2521 . 4 kJ/mol of rxn 7.- 520 . 2 kJ/mol of rxn Explanation: The balanced equations for standard heats of combustion are CH 4 (g) + 2 O 2 (g)- CO 2 (g) + 2 H 2 O( ) H =- 890 kJ / mol perlick (app582) Homework #1 holcombe (51160) 2 CO(g) + 1 2 O 2 (g)- CO 2 (g) H =- 283 kJ / mol The desired reaction can be obtained by doubling the first reaction and then adding it to twice the reverse of the second reaction: 2 CH 4 (g) + 4 O 2 (g)- 2 CO 2 (g) + 4 H 2 O( ) H = 2(- 890 kJ / mol) =- 1780 kJ / mol 2 CO 2 (g)- 2 CO(g) + O 2 (g) H = 2(283 kJ / mol) = 566 kJ / mol 2 CH 4 (g) + 3 O 2 (g)- 2 CO(g) + 4 H 2 O( ) H =- 1214 kJ / mol 005 10.0 points Calculate the standard reaction enthalpy for the oxidation of nitric oxide to nitrogen dioxide 2 NO(g) + O 2 (g) 2 NO 2 (g) given N 2 (g) + O 2 2 NO(g) H = +180 . 5 kJ mol 1 2 NO 2 (g) N 2 (g) + 2 O...
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This note was uploaded on 02/07/2012 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

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CH 302 Holcombe Hwk #1 - perlick (app582) Homework #1...

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