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worksheet 11 key - Fall 2010 CH301 Worksheet 11 Answer Key...

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Fall 20 10 CH301 Worksheet 1 1 Answer Key: Thermodynamic Calculations for Chemical Reactions and Phase Changes Check for explanation of solution key at bottom of page—Assume T = 298K. First describe the reaction below where it is written, then predict the sign for each answer and only then, do the calculation. The BE values are at the bottom of the worksheet. The formation constants are found in the textbook appendix and also as Worksheet 1 1a. This worksheet is painful at first, but once you get it you are a profoundly better chemist (and exam 3 test taker.) Chemical Reaction Δ H (kJ) BE (kJ) Δ n gas w (kJ)= - Δ nRT Δ n system ΤΔ S (kJ) Δ G (kJ) CH 4 g + 2O 2 g Æ CO 2 g + 2H 2 Og Combustion reaction, would predict large heat and spontaneous reaction. Δ n = 0 means no work, small entropy change. -802 -802 0 0 0 -1 -801 2H 2 g + O 2 g Æ 2H 2 Og Spontaneous combustion reaction, would predict large heat. Δ n = negative which means entropy decreases -484 -482 - 1 +2.5 -1 -27 -458 C 2 H 5 OH l + 3O 2 g Æ 2CO 2 g + 3H 2 Og Spontaneous combustion reaction, would predict large heat. Δ n = is positive so work on surroundings and positive entropy. -1234 -1248 2 -5 1 66 -1300 C 2 H 5 OH l + 3O 2 g Æ 2CO 2 g + 3H 2 O l Combustion reaction, would predict large heat and spontaneous reaction.
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