ycs73 – Homework 11 – Fakhreddine – (53605) 1 This print-out should have 14 questions. Multiple-choice questions may continue on the next column or page – fnd all choices be±ore answering. 001 10.0 points Which o± the ±ollowing statements about re-acting molecules is true? 1. An e²ective 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 specifc temperature have the same energy. 4. The transition state energy is usually the average between the energies o± the reactants and products. Explanation: A collision between molecules results in a reaction i± they collide with enough energy and an e²ective orientation. 002 10.0 points Activation energy ±or an elementary process 1. is smaller ±or slower reactions and larger ±or ±aster reactions. 2. is part o± the net enthalpy change ±or the reaction. 3. is the energy required to produce the transition state ±rom the reactants. correct 4. None o± these Explanation: E a reactants products transition state Reaction progress Potential energy When the reactants gain enough energy to equal the energy o± activation the transition state is ±ormed. 003 (part 1 o± 2) 10.0 points Consider the ±ollowing potential energy dia-gram. 40 80 120 160 energy, kJ reaction progress A + B AB What is the value o± Δ H ? Correct answer: − 10 kJ. Explanation: The fnal energy ±or AB is 20 kJ. The initial energy ±or A + B is 30 kJ. Δ H = fnal − initial = 20 − 30 = − 10 kJ 004 (part 2 o± 2) 10.0 points What is the activation energy E a ±or this re-action? Correct answer: 150 kJ. Explanation: The maximum energy (top o± “hill”) is 180 kJ. The initial energy ±or 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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