Homework 11

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Unformatted text preview: ycs73 Homework 11 Fakhreddine (53605) 1 This print-out should have 14 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Which of the following statements about re- acting molecules is true? 1. An effective collision between two molecules must be oriented correctly. cor- rect 2. When two reactant molecules collide they must react. 3. All molecules in a gas sample at a specific temperature have the same energy. 4. The transition state energy is usually the average between the energies of the reactants and products. Explanation: A collision between molecules results in a reaction if they collide with enough energy and an effective orientation. 002 10.0 points Activation energy for an elementary process 1. is smaller for slower reactions and larger for faster reactions. 2. is part of the net enthalpy change for the reaction. 3. is the energy required to produce the transition state from the reactants. correct 4. None of these Explanation: E a reactants products transition state Reaction progress Potentialenergy When the reactants gain enough energy to equal the energy of activation the transition state is formed. 003 (part 1 of 2) 10.0 points Consider the following potential energy dia- gram. 40 80 120 160 energy,kJ reaction progress A + B AB What is the value of H ? Correct answer: 10 kJ. Explanation: The final energy for AB is 20 kJ. The initial energy for A + B is 30 kJ. H = final initial = 20 30 = 10 kJ 004 (part 2 of 2) 10.0 points What is the activation energy E a for this re- action? Correct answer: 150 kJ. Explanation: The maximum energy (top of hill) is 180 kJ. The initial energy for A + B is 30 kJ. ycs73 Homework 11 Fakhreddine (53605) 2 E a = maximum initial = 180 30 = 150 kJ 005 10.0 points The overall reaction NO 2 (g) + CO(g) NO(g) + CO 2 (g) is proposed to proceed by the mechanism 2 NO 2 (g) NO 3 (g) + NO(g) slow NO 3 (g) + CO(g) NO 2 (g) + CO 2 (g) fast Which of the following rate laws would be...
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