Final - Spring 2008

Final - Spring 2008 - Name Chem 0120 Golde Sections Spring...

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Name ________________________ Signature ____________________ Chem 0120 - Golde Sections FINAL EXAM Spring Term 2008 Wednesday, April 23 INSTRUCTIONS DO NOT TEAR ANY PAGES OFF YOUR EXAM, EXCEPT THE LAST PAGE. PRINT AND SIGN YOUR NAME AT THE TOP OF THIS PAGE. The exam contains 29 multiple-choice questions (6 points each) to be answered on the machine-scored sheet, using a soft pencil. Be sure to write and code in your name on this sheet (last name – space - first name). Do all your working on the exam sheets. Answer Question 30 (8 points) on the exam sheet. *** The last 18 points will be given for your written answers to questions marked *** in the exam. An answer key will be available in Room 101 Chevron after the exam (about 1pm). It will also be posted on our Courseweb site. USEFUL INFORMATION SEE BACK PAGE GOOD LUCK GOOD LUCK GOOD LUCK ***Have you answered the QUESTION??*** ***Does your Answer MAKE SENSE??***
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USEFUL INFORMATION G = H - T ⋅∆ S Charge = current x time G ° = -RT ln K R = 8.31 J/mol K G = G ° + RT ln Q G ° = -nE ° F F = 96,500 Coul/mol e - E = E ° - 0.0257 n n Q 0 ° C = 273 K t 0 [A] ln [A] = -kt ln 1 2 k k = E R T T T T a 2 1 1 2 - t ½ = ln 2 k or ln 1 2 k k = 2 1 a T 1 - T 1 R E HA + H 2 O H 3 O + + A - , K c = K a K c = K a x K b /K w pH = -log 10 [H 3 O + ] M = mol/L K w = 1.0 x 10 -14 = [H 3 O + ] [OH - ] K w = K a .K b Avogadro’s Number = 6.02 x 10 23 /mol 6.02 x 10 23 amu = 1 g For ax 2 + bx + c = 0, x = - ± - b b ac a 2 4 2 > means greater than; < means less than
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Equilibria, Acids and Bases and Solubility 1. Given the following reactions and equilibrium constants, K c : PO 4 3- (aq) + H 2 O(l) HPO 4 2- (aq) + OH - (aq), K c1 = 2.1 x 10 -2 NH 4 + (aq) + H 2 O(l) NH 3 (aq) + H 3 O + (aq), K c2 = 5.6 x 10 -10 Determine the equilibrium constant of: NH 4 + (aq) + PO 4 3- (aq) NH 3 (aq) + HPO 4 2- (aq), K c3 = ? *** Show your work or give your reasoning a) c1 c2 w 1 K x K x K = 8.5 x 10 24 b) K c1 x K c2 x K w = 1.2 x 10 -25 c) w 1 K = 1.0 x 10 14 d) c1 c2 1 K x K = 8.5 x 10 10 e) c1 c2 w K x K K = 1.2 x 10 3 2. Consider the reaction: N 2 (g) + 3 H 2 (g) 2 NH 3 (g). In a certain test of this reaction, the initial pressures were: N 2 : 0.57atm; H 2 : 2.46atm; NH 3 : 0.320atm. At equilibrium , the H 2 pressure was 1.11atm. Determine the pressures of N 2 and NH 3 at equilibrium. p(N 2 ) atm p(NH 3 ) atm a) 0.12 1.67 b) 1.02 0.90 c) 1.02 0.62 d) 0.45 0.90 e) -0.78 1.67 f) 0.12 1.22
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3. For each of the following reactions, assign the equilibrium constant, K c , as large (>> 1, e.g. 1 x 10 5 ) or small (<< 1, e.g. 1 x 10 -5 ). I. H 3 O + (aq) + OH - (aq) H 2 O + H 2 O II. CN - (aq) + H 3 O + (aq) HCN(aq) + H 2 O III. C 2 H 5 COOH(aq) + H 2 O C 2 H 5 COO - (aq) + H 3 O + (aq) I II III a) Large Small Large b) Small Large Small c) Large Small Small d) Large Large Small e) Small Small Large
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