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Unformatted text preview: Yoon, Seong Meen – Homework 11 – Due: Dec 5 2007, 11:00 pm – Inst: James Holcombe 1 This print-out should have 28 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points For a reaction that is zero-order overall, 1. the rate does not change during the reac- tion. correct 2. the rate constant is zero. 3. the activation energy is zero. 4. the reactant concentration does not change with time. Explanation: Remember that for a zero order reaction, the reactant is still used up; its concentration will decrease as time passes, but the rate will not be affected. If you double or triple the concentration of that reactant, the rate will not change for a zero order reaction. 002 (part 1 of 1) 10 points The rate of the reaction 2O 3 → 3O 2 is equal to 1.- 1 2 Δ[O 3 ] Δ t . correct 2.- 1 3 Δ[O 2 ] Δ t . 3. + 1 2 Δ[O 3 ] Δ t . 4.- Δ[O 3 ] Δ t . 5.- Δ[O 2 ] Δ t . Explanation: The rate of a chemical reaction can either be expressed as the rate of disappearance of a reactant (as in this case) or as the rate of appearance of a product. However, this rate is multiplied by the inverse of the coef- ficient of the species in question. The nega- tive sign here reminds us that as the reaction progresses, this species is consumed and de- creases in concentration. 003 (part 1 of 1) 10 points When we speak of the rate of a reaction, we are referring to 1. the instantaneous rate. correct 2. the integrated rate. 3. the minimum rate. 4. the average rate. 5. the maximum rate. Explanation: Reaction rate varies as a reaction pro- gresses, slowing down as the amount of re- actant decreases. The instantaneous rate is the rate at a particular time. 004 (part 1 of 1) 10 points Consider the elementary reaction H + Br 2 → HBr + Br The rate of production of HBr would be reliably aproximated as simple first order if 1. [H] is small and [Br 2 ] is small. 2. [H] and [Br 2 ] are about equal. 3. [H] is small and [Br 2 ] is large. correct 4. first order will never be a good approxi- mation. 5. [H] is large and [Br 2 ] is large. Explanation: The very small amount of H will be con- tinuously used up, displacing one of the Br atoms and forming HBr. Yoon, Seong Meen – Homework 11 – Due: Dec 5 2007, 11:00 pm – Inst: James Holcombe 2 005 (part 1 of 1) 10 points Consider the reaction 2NO 2 (g) + F 2 (g) → 2NO 2 F(g) rate =- Δ[F 2 ] Δ t . What is another form of the rate of the reaction? 1. Δ[NO 2 F] 2Δ t correct 2.- Δ[NO 2 ] Δ t 3. Δ[NO 2 F] Δ t 4. Δ[NO 2 ] 2Δ t 5.- 2Δ[NO 2 ] Δ t Explanation: 006 (part 1 of 1) 10 points For the reaction 2NO(g) + 2H 2 (g) → N 2 (g) + 2H 2 O(g) the following data were collected....
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This note was uploaded on 05/14/2009 for the course CH 53575 taught by Professor Hackert during the Spring '09 term at University of Texas.
- Spring '09