spring 06 exam 2

spring 06 exam 2 - 1 SPRING 2006 CHEM 110 EXAM 2 SHOW ALL...

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SPRING 2006 CHEM 110 EXAM 2 – SHOW ALL WORK – NO WORK, NO CREDIT 1. (15 pts) (a) When one mole of ice is frozen at –10 ºC, what are the relative values of Δ S sys and Δ S surr ? Is the reaction spontaneous? (i) ΔS sys > 0, ΔS surr < 0, spontaneous (ii) ΔS sys > 0, ΔS surr < 0, non-spontaneous (iii) ΔS sys > 0, ΔS surr < 0, equilibrium (iv) ΔS sys < 0, ΔS surr > 0, spontaneous (v) ΔS sys < 0, ΔS surr > 0, non-spontaneous (vi) ΔS sys < 0, ΔS surr > 0, equilibrium (b) Predict which compound has more entropy ( circle your choice in each, no calculation needed ). (i) OR OR Can’t Predict (ii) Cl 2 ( g ) OR Br 2 ( g ) OR Can’t Predict (c) For the following reaction, do the reactants or the products have more entropy? CO 2 ( g ) + C ( s ) → 2 CO ( g ) Reactants OR Products OR Can’t Predict (d) Potassium chlorate, one of the common oxidizing agents in explosives, fireworks, and match heads, undergoes a solid-state redox reaction when heated. Calculate the total entropy change at 25 ºC and state whether or not this reaction occurs spontaneously at this temperature. 4 KClO 3 ( s ) → 3 KClO 4 ( s ) + KCl ( s ) Δ H º rxn = –144 kJ Δ S º rxn = –36.8 J/K __________ J/K Spontaneous? ( circle one ) Yes No 1
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SPRING 2006 CHEM 110 EXAM 2 – SHOW ALL WORK – NO WORK, NO CREDIT 2. (10 pts) (a) Oxyacteylene welding is a common method for repairing metal structures, including bridges, buildings, and even the Statue of Liberty. Calculate Δ G o at 700 ºC for the combustion of 1 mol acetylene C 2 H 2 . (Δ H o rxn = –2599 kJ; Δ S o rxn = – 433.13 J/K) 2 C 2 H 2 ( g ) + 5 O 2 ( g ) → 4 CO 2 ( g ) + 2 H 2 O ( l ) Δ G o = __________ kJ (b) Butane is a common fuel used in cigarette lighters and camping stoves. Normally supplied in metal containers under pressure, the fuel exists as a mixture of liquid and gas, so high temperatures may cause the container to explode.
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This note was uploaded on 04/12/2008 for the course CHEM 109 taught by Professor Malina during the Spring '08 term at UNL.

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spring 06 exam 2 - 1 SPRING 2006 CHEM 110 EXAM 2 SHOW ALL...

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