230_Sp10_E2_key(1) - CHEM 230 Sp 10 Exam 2 p1 Name:_ 1) A...

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CHEM 230 Sp 10 Exam 2 p1 Name:__________________________ a) T b = 101.12 o C b) vapor pressure 16.87 torr c) osmotic pressure 0.0406 atm 1) A molecular solute (MW = 180.16) is added to water. The resulting solution has a freezing point of -4.1 o C and a density of 1.07 g/mL. k f H2O = 1.86 (K kg)/mol; k b H2O = 0.51 (K kg)/mol; vapor pressure of water @293K = 17.54 torr a) ( 4pts ) What is the boiling point of the solution? " T f = k f m " T b = k b m " T f k f = m = " T b k b = m 4.1 1.86 = " T b 0.51 1.12 = " T b T b = 101.12 o C b) ( 8pts ) What is the vapor pressure of the solution (in torr) @293K? " T f = k f m 4.1K =1.86 Kmol kg m 2.204 mol kg = m = 2.204 molsolute kgH 2 O Assume 1 kg H 2 O * 1000 g 1 kg * 1 mol 18 g = 55.56 molH 2 O P = x H 2 O P pure = 55.56 molH 2 O 55.56 molH 2 O + 2.204 molsolute *17.54 torr = 16.87 torr c) ( 8pts ) What is the osmotic pressure of the solution (in atm) @ 293K? 1 kgH 2 O = 1000 g 2.204 mol 180.16 g 1 mol " # $ % = 397.07 g 1397.07 gtotal mL 1.07 g " # $ % = 1305.7 mL c = 2.204 molsolute 0.13057 L = 0.00169 M ( = RTc = 0.08206 Latm Kmol 293 K ( ) 0.00169 mol L " # $ % 0.0405 atm
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CHEM 230 Sp 10 Exam 2 p2 Name:__________________________ 2) Ed showed you a demo of the following equilibrium in class. CoCl 4 2- (aq) Co +2 (aq) + 4Cl - (aq) c) ( 4pts ) CoCl 4 2- (aq) is a blue complex. Co +2 (aq) forms a pink complex. (Chloride is colorless.) When Ed cooled down the blue solution it turned pink. Is the Δ H of the reaction greater than, equal to, or less than 0? ( Circle one.) Δ H > 0 H= 0 H <0 d) ( 4pts ) When Ed added HCl which direction did the equilibrium shift? ( Circle one ) towards the reactants towards the products a) ( 2 pts ) One of the stresses that he put on the system was the addition of water. According to the chemical equation above, which direction did the equilibrium shift when water was added? ( Circle one ) towards the products towards the reactants b) ( 4pts ) Explain why the equilibrium shifted in that direction upon addition of water.
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This note was uploaded on 01/24/2012 for the course PCHEM 230 taught by Professor Gottfried during the Fall '11 term at University of Michigan.

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230_Sp10_E2_key(1) - CHEM 230 Sp 10 Exam 2 p1 Name:_ 1) A...

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