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Chem 102 Fall Exam 2 - Name_Mr Perfect Date_F 13 1...

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Name _____Mr. Perfect_____________________________________ Date ______F 13_____________ Chemistry 102 Exam 2 1. Calculate the pH and percent dissociation for an aqueous 1.5 M H NO 2 solution. (10 pts) K a = 4.5 x 10 -4 for H NO 2 HNO 2 H + + NO 2 - I 1.5 0 0 C -x +x +x E 1.5 x x x x = 2.60 x 10 -2 M = [H + ] Check: pH = -log (2.60 x 10 -2 ) = 1.59 2. Aniline (C 6 H 5 NH 2 ) is an organic base used to manufacture dyes. Calculate the pH of a 0.15 M solution of aniline. { Hint : C 6 H 5 NH 2 + H + C 6 H 5 NH 3 + } (10 pts) K b = 4.3 x 10 -10 C 6 H 5 NH 2 + H 2 O C 6 H 5 NH 3 + + OH - I 0.15 --- 0 0 C -x --- +x +x E 0.15 x --- x x pOH = -log(8.03 x 10 -6 ) = 5.10 pH = 14 5.10 = 8.90 3. Calculate the pH of a 0.25 M C 5 H 5 N H Cl salt solution. (10 pts) K b =1.7 x 10 -9 for C 5 H 5 N C 5 H 5 N H C 5 H 5 N + H + I 0.25 --- 0 0 C -x --- +x +x E 0.25 x --- x x pH = -log(1.21 x 10 -3 ) = 2.92
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Name _____Mr. Perfect_____________________________________ Date ______F 13_____________ Chemistry 102 Exam 2 4. Carbonic acid (H 2 CO 3 ) is used to buffer blood. Use the Henderson-Hasselbalch equation to calculate the ratio of HCO 3 - to H 2 CO 3 in blood having a pH of 7.40. (10 pts) K a1 = 4.3 x 10 -7 and K a2 = 5.6 x 10 -11 H 2 CO 3 H + + HCO 3 - 5. Methyl red is an indicator used in titrations and has a K a equal to 7.9 x 10
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