CH 302 HW11 - Thompson Margaret Homework 11 Due Dec 5 2007...

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Thompson, Margaret – 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 activation energy is zero. 2. the rate constant is zero. 3. the reactant concentration does not change with time. 4. the rate does not change during the reac- tion. correct 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 2 O 3 3 O 2 is equal to 1. - 1 2 Δ[O 3 ] Δ t . correct 2. - Δ[O 2 ] Δ t . 3. + 1 2 Δ[O 3 ] Δ t . 4. - Δ[O 3 ] Δ t . 5. - 1 3 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 maximum rate. 2. the integrated rate. 3. the minimum rate. 4. the average rate. 5. the instantaneous rate. correct 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 large and [Br 2 ] is large. 2. [H] and [Br 2 ] are about equal. 3. [H] is small and [Br 2 ] is large. correct 4. [H] is small and [Br 2 ] is small. 5. first order will never be a good approxi- mation. Explanation: The very small amount of H will be con- tinuously used up, displacing one of the Br atoms and forming HBr.
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Thompson, Margaret – Homework 11 – Due: Dec 5 2007, 11:00 pm – Inst: James Holcombe 2 005 (part 1 of 1) 10 points Consider the reaction 2 NO 2 (g) + F 2 (g) 2 NO 2 F(g) rate = - Δ[F 2 ] Δ t . What is another form of the rate of the reaction? 1. - Δ[NO 2 ] Δ t 2. Δ[NO 2 ] 2 Δ t 3. Δ[NO 2 F] Δ t 4. - 2 Δ[NO 2 ] Δ t 5. Δ[NO 2 F] 2 Δ t correct Explanation: 006 (part 1 of 1) 10 points For the reaction 2 NO(g) + 2 H 2 (g) N 2 (g) + 2 H 2 O(g) the following data were collected. [NO(g)] [H 2 (g)] Rate, M/s 0.10 0.10 0.0050 0.10 0.20 0.010 0.10 0.30 0.015 0.20 0.10 0.020 0.20 0.20 0.040 What is the rate law for this reaction? 1. rate = k [H 2 ] [NO] 2. rate = k [H 2 ] 2 [NO] 3. rate = k [H 2 ] [NO] 4. rate = k [H 2 ] [NO] 2 5. None of these 6. rate = k [H 2 ] [NO] 2 correct Explanation: 007 (part 1 of 3) 10 points Manganate ions (MnO 2 - 4 ) react at 2.0 mol L · min in acidic solution to form per- manganate ions and manganese(IV) oxide: 3 MnO 2 - 4 (aq) + 4 H + (aq) 2 MnO - 4 (aq) + MnO 2 (s) + 2 H 2 O( )
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