hw1solution_pdf

# hw1solution_pdf - So(dds785 – Homework 1 – Sutcliffe...

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Unformatted text preview: So (dds785) – Homework 1 – Sutcliffe – (52440) 1 This print-out should have 18 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points If the reaction quotient Q for some hypothet- ical reaction is 100, how does Δ G compare to Δ G ? 1. Δ G < Δ G 2. Δ G = Δ G 3. There is insufficient information given to determine the answer. 4. Δ G > Δ G correct Explanation: Δ G = Δ G + RT ln Q If Q = 100, then the natural log term will be positive. This means that the non standard value of Δ G will be bigger (more positive) than the value of Δ G . 002 10.0 points If Δ G ◦ = 27 . 1 kJ at 25 ◦ C for the reaction CH 3 COOH(aq) + H 2 O( ℓ ) → CH 3 COO − (aq) + H 3 O + (aq) , calculate K a for this reaction at 298 K. 1. 1 . 78 × 10 − 5 correct 2. 5 . 63 × 10 4 3. 1.01 4. 9 . 89 × 10 − 1 5. 1 . 15 × 10 − 11 Explanation: 003 10.0 points WITHDRAWN 004 10.0 points The standard state for phosphorus is white phosphorus. (There’s a red form too, but thats not the standard). What is the numerical value of the equi- librium constant K p at 25 ◦ C for the de- composition of phosgine (PH 3 ) gas into the elements white phosphorus and hydrogen? Δ G f = 13 . 4 kJ / mol for PH 3 (g). 1. 9 . 95 × 10 − 1 2. 1 . 00 × 10 1 3. None of these 4. 4 . 48 × 10 − 3 5. 2 . 23 × 10 2 correct Explanation: Δ G =- 13 . 4 kJ / mol =- 13400 J / mol T = 25 ◦ C = 298 K R = 8 . 314 J mol · K K p = e − Δ G/ ( R T ) = exp bracketleftBigg 13400 J / mol (8 . 314 J mol · K ) (298 K) bracketrightBigg = 223 . 301 005 10.0 points A group who investigated the formation of ammonia from its elements determined that K c is 90 at 773 K and 3 at 873 K. Is this reaction endothermic or exothermic? 1. Cannot tell; insufficient information is given. 2. endothermic 3. exothermic correct 4. Neither; the reaction is at equilibrium. Explanation: The K is observed to decrease with increas- ing temperature of reaction, which is charac- teristic of exothermic reactions. 006 10.0 points Which of the following reactions’ equilibrium So (dds785) – Homework 1 – Sutcliffe – (52440) 2 constants (K) would exhibit the greatest tem- perature dependence?...
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hw1solution_pdf - So(dds785 – Homework 1 – Sutcliffe...

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