ProblemSet_9 - CHEM 3615 Problem Set #9 – Properties of G...

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Unformatted text preview: CHEM 3615 Problem Set #9 – Properties of G and Phase Diagrams Due November 6, 2007 (don't forget to vote) Read Chapters 4 and 5. All six problems are due at the start of class and will be graded. 1. Consider the following reaction: CH 3 COOH (l) + C 2 H 5 OH (l) → CH 3 COOC 2 H 5 (l) + H 2 O (g) (I) Plot Δ r G(T) vs. T for assuming Δ r H o and Δ r S o are independent of temperature for T = 0 to 400 K. Now do the same thing assuming liquid water instead of gas is released. CH 3 COOH (l) + C 2 H 5 OH (l) → CH 3 COOC 2 H 5 (l) + H 2 O (l) (II) Which reaction shows the stronger temperature dependence for Δ r G(T) ? Demonstrate this by plotting Δ r G(T) vs. T on the same graph for Reactions I & II. Also comment on which temperatures lead to a spontaneous, non-spontaneous, or equilibrium reaction for the forward reaction. Solution: Reaction I: CH 3 COOH (l) + C 2 H 5 OH (l) → CH 3 COOC 2 H 5 (l) + H 2 O (g) ΔH o f (kJ • mol −1 ) -484.5 - 277.69 -479.0 -241.82 S o (J •mol −1 K −1 ) 159.8 160.7 259.4 188.83 Δ r H o = ∑ν i ΔH f o ,i =−241.82 − 479.0 + 277.69 + 484.5 = 41.37kJ • mol −1 Δ r S o = ∑ν i S i o = 188.83 + 259.4 −160.7 −159.8 = 127.73J • mol −1 • K −1 = 0.12773kJ • mol −1 • K −1 oo −1 −1 −1 Δ G(T) =Δ H − TΔ S = 41.37kJ • mol − ( 0.12773kJ • mol • K )× T r rr Reaction II: CH 3 COOH (l) + C 2 H 5 OH (l) → CH 3 COOC 2 H 5 (l) + H 2 O (l) ΔH o f (kJ • mol −1 ) -484.5 -277.69 -479.0 -285.83 S o (J •mol −1 K −1 ) 159.8 160.7 259.4 69.91 Δ r H o =∑ν i ΔH f o ,i =−285.83 − 479.0 + 277.69 + 484.5 =−2.64kJ • mol −1 Δ r S o = ∑ ν i S i o = 69.91+ 259.4 −160.7 −159.8 = 8.81J • mol −1 • K −1 = 0.00881kJ • mol −1 • K −1 oo −1 −1 −1 Δ G(T) =Δ H − TΔ S =−2.64kJ • mol − ( 0.00881kJ • mol • K )× T r rr ffd8ffe000104a46494600010201007800780000ffe20c584943435f50524f46494c4500010100000c484c696e6f021000006d6e7472 5247422058595a2007ce00020009000600310000616373704d53465400000000494543207352474200000000000000000000000000 00f6d6000100000000d32d485020200000000000000000000000000000000000000000000000000000000000000000000000000000 0000000000000000001163707274000001500000003364657363000001840000006c77747074000001f000000014626b7074000002 04000000147258595a00000218000000146758595a0000022c000000146258595a0000024000000014646d6e640000025400000070 646d6464000002c400000088767565640000034c0000008676696577000003d4000000246c756d69000003f8000000146d65617300 00040c0000002474656368000004300000000c725452430000043c0000080c675452430000043c0000080c625452430000043c0000 080c7465787400000000436f70797269676874202863292031393938204865776c6574742d5061636b61726420436f6d70616e7900 00646573630000000000000012735247422049454336313936362d322e310000000000000000000000127352474220494543363139 36362d322e31000000000000000000000000000000000000000000000000000000 The plot of Δ r G(T) vs. T are shown as follows (note the dashed line indicates zero): Reaction I has a larger temperature dependence. Why? Gas Reaction I has a larger temperature dependence....
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This note was uploaded on 04/30/2008 for the course CHEM 3615 taught by Professor Aresker during the Fall '07 term at Virginia Tech.

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ProblemSet_9 - CHEM 3615 Problem Set #9 – Properties of G...

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