HW8solutions - Niu (qn269) – Homework 8 – flowers –...

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Unformatted text preview: Niu (qn269) – Homework 8 – flowers – (53885) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. HW 8. Due 25 November 2008 at 11PM 001 10.0 points The rate of formation of oxygen in the follow- ing reaction is 2.28 M/s. 2 N 2 O 5 (g) → 4 NO 2 (g) + O 2 (g) What is the rate of formation of NO 2 ? 1. 1.14 M/s 2. 2.28 M/s 3. 9.12 M/s correct 4. 0.57 M/s 5. 4.56 M/s Explanation: The NO 2 forms at 4 × the rate of the O 2 . 002 10.0 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 F] Δ t 2. Δ[NO 2 F] 2 Δ t correct 3. Δ[NO 2 ] 2 Δ t 4. − Δ[NO 2 ] Δ t 5. − 2 Δ[NO 2 ] Δ t Explanation: 003 10.0 points Consider the concentration-time dependence as shown below for two first order reactions. [A] Molar Concentration of Reactant Concentration −→ Time −→ Which reaction has the greatest t 1 / 2 ? 1. the reaction represented by the lower curve 2. the reaction represented by the upper curve correct 3. Unable to determine Explanation: 004 10.0 points One of the reactions used commercially to produce hydrogen gas is H 2 O(g) + CO(g) → H 2 (g) + CO 2 (g) . A proper expression for the rate of this reaction could be 1. − Δ[CO 2 ] Δt . 2. + Δ[CO] Δt . 3. − Δ[H 2 O] Δt . correct 4. − Δ[H 2 ] Δt . Explanation: Niu (qn269) – Homework 8 – flowers – (53885) 2 The rate of a chemical reaction can either be expressed as the rate of disappearance of the reactant (as in this case) or as the rate of the appearance of the product; however, this rate is multiplied by the inverse of the coefficient of the species in question. The negative sign here reminds us that as the reaction progresses, this species is consumed and goes down in concentration. 005 10.0 points What is the rate for the formation of Cu(s) in the reaction Cu 2+ (aq) + H 2 (g) ⇀ ↽ Cu(s) + 2 H + (aq) if Δ[H + ] Δ t = 1 . 2 × 10 − 3 ? 1. 2 × 10 − 4 2. 2 . 4 × 10 − 3 3. 3 × 10 − 4 4. 1 . 2 × 10 − 3 5. 6 × 10 − 4 correct Explanation: 006 10.0 points What is the rate law for the reaction A + B + C → D if the following data were collected? Exp [A] [B] [C] Initial Rate 1 0.4 1.2 0.7 2 . 32 × 10 − 3 2 1.3 1.2 0.9 7 . 54 × 10 − 3 3 0.4 4.1 0.8 9 . 25 × 10 − 2 4 1.3 1.2 0.2 7 . 54 × 10 − 3 1. rate = 3 . 36 × 10 − 3 [A] 1 [B] 3 [C] correct 2. rate = 1 . 79 × 10 − 3 [A] [B] 2 [C] 1 3. rate = 1 . 49 × 10 − 3 [A] [B] 3 [C] 1 4. rate = 4 . 48 × 10 − 3 [A] 1 [B] 2 [C] 1 5. rate = 5 . 37 × 10 − 3 [A] 1 [B] 3 [C] Explanation: 007 10.0 points For a given reaction, the rate-law is 1. an equation in which reaction rate is equal to a mathematical expression involving con- centrations of reactants. correct 2. a constant of proportionality between re- action rate and the concentrations of reac- tants....
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This note was uploaded on 02/04/2009 for the course CH 53885 taught by Professor Flowers during the Fall '08 term at University of Texas.

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HW8solutions - Niu (qn269) – Homework 8 – flowers –...

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