eng-08spring-CHM2046C-e102x04-key

eng-08spring-CHM2046C-e102x04-key - Exam 4 answer key The...

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Exam 4 answer key 18 Apr 08 The test version is listed after before problem #1, after #14 and next to #15. PART I (49 pts total, each question is 3.5 pts) The “date covered” is the lecture date for that material. #12’s correct answer #12 (1.35 × 10 -12 J/nucleon) was not listed, so everyone will get credit for that problem. PART II (51 pts possible) Indicator colors at various pH’s (6 pts – 1 pt each blank, covered March 28 ) Below are common acid-base indicators, their K a ’s, and the colors of their un-ionized forms and ionized forms. indicator K a (at 25 °C) un-ionized color ionized color methyl orange 3.47 × 10 -4 red orange-yellow alizarine yellow R 6.31 × 10 -12 yellow brown-red Determine the colors of the indicators at these pH values at 25 °C. Find the pKa’s (methyl orange, 3.46; alizarine yellow R, 11.2) and compare with the pH. If the pH is lower than the pK a , the indicator is in its un-ionized acidic form. If the pH is higher than the pKa, the indicator is in its ionized basic form. ι -4-B and θ -4-B indicator pH = 2.0 pH = 7.0 pH = 10.0 methyl orange red orange-yellow orange-yellow alizarine yellow R yellow yellow yellow ι -4-C and θ -4-C indicator pH = 5.0 pH = 7.0 pH = 9.0 methyl orange orange-yellow orange-yellow orange-yellow alizarine yellow R yellow yellow yellow # Question Date(s) covered Percent Correct ι -4- B ι -4- C θ -4- B θ -4- C 1 K b from graph of a weak acid titration 3/26, 3/28, lab 37.1 a c e d 2 K sp : concentration in a saturated solution 3/28 34.3 b b a d 3 common ion effect 3/28 & 3/31 48.6 c d e b 4 K f (manipulating K’s) 3/31 (& 2/25) 42.9 b e d a 5 solubility of a salt and pH 3/31 25.7 d a e c 6 reducing agent 4/2 37.1 d c b e 7 reduction potentials (NW-SE rule) 4/7 74.3 e e d a 8 purpose of a salt bridge 4/4 48.6 b d d b 9 electrolysis 4/9 25.7 e b a d 10 nuclear chemistry ideas 4/9 to 4/16 22.9 e c d b 11 belt of stability 4/11 37.1 d e c a 12 E = mc 2 4/14 100% 13 nuclear kinetics 4/14 74.3 a d e b 14 oxidation # in a coordination compound 4/2 & 4/16 25.7 d c e a
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This note was uploaded on 07/10/2011 for the course CHM 2045 taught by Professor Eng during the Fall '10 term at UNF.

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eng-08spring-CHM2046C-e102x04-key - Exam 4 answer key The...

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