Spring '11 Exam 3 with Answers

A 13 kjmol reverse b 13 kjmol forward c 012 kjmol

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A. 1.3 kJ/mol; reverse B. 1.3 kJ/mol; forward C. -0.12 kJ/mol; reverse D. -0.12 kJ/mol; forward E. 0 kJ/mol; the reaction is at equilibrium BONUS QUESTION (7.5 points) 21. Consider the triprotic phosphoric acid, H 3 PO 4 . As you already know from Chapter 16, acidic protons dissociate from polyprotic acids one after another: rxn. 1 H 3 PO 4 (aq) + H 2 O( l ) H 3 O + (aq) + H 2 PO 4 - (aq) K a1 = 5.5 × 10 - 3 at 25 °C rxn. 2 H 2 PO 4 - (aq) + H 2 O( l ) H 3 O + (aq) + HPO 4 2 - (aq) K a2 = 6.2 × 10 - 8 at 25 °C rxn. 3 HPO 4 2 - (aq) + H 2 O( l ) H 3 O + (aq) + PO 4 3 - (aq) K a3 = 4.8 × 10 - 13 at 25 °C What is the correct order (from the most negative/least positive to the least negative/most positive) of standard Gibb’s free energy changes that correspond to the above dissociation processes? A. Δ G o rxn1 < Δ G o rxn2 < Δ G o rxn3 B. Δ G o rxn3 < Δ G o rxn2 < Δ G o rxn1 C. Δ G o rxn2 < Δ G o rxn1 < Δ G o rxn3 D. Δ G o rxn3 < Δ G o rxn1 < Δ G o rxn2 E. Δ G o rxn1 < Δ G o rxn3 < Δ G o rxn2
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8 FROM 1: 1C, 2E, 3B, 4A, 5E, 6D, 7A, 8B, 9D, 10C, 11A, 12D, 13C, 14B, 15C, 16E, 17A, 18E, 19E, 20A, 21A
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