Chapter_12_and_13_Office_Hour_Packet_Answers

Chapter_12_and_13_Office_Hour_Packet_Answers - Answers to...

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Unformatted text preview: Answers to 12 and 13 1. ΔT = T f- T i = -K f im solute Solute = 20 g Benzene = 500 g T f = 3.77 T i = 5.48 K f = 5.12 (3.77 - 5.48) = -5.12 x 1 x ((20g/MW)/500 g) x 1000 g/kg MW = 119.8 g, A 2. Henry’s Law: X A =kP A mol CO 2 /(mol CO 2 + mol H 2 O) = 6.1 x 10-4 x 1.1 Y/(Y + (0.50L x 1000 g/L x (1 mol/18.02 g))) = (6.1 x 10-4 x 1.1) Y = 0.0186 mol CO 2 Based on the very small constant, the above calculation assumed that the moles of CO2 dissolved in the club soda was insignificant, i.e., that all of the 0.50 L of club soda is water. Proof that this assumption is valid is that 0.0186 mol CO 2 is only 0.07% of the 0.50 L of H 2 O. However, it wasn’t necessary to make this assumption. In the calculation the moles of CO 2 could have been subtracted from the moles of H 2 O : ((Y)/(Y + (0.50 x 1000 x (1/18.02) – Y))) = (6.1 x 10-4 x 1.1) Y = 0.0186 mol CO 2 3. Raoult’s Law: P soln = X solvent P o solvent mol H 2 O = 200g/18.02gmol-1 = 11.099 mol P soln = ((11.099 mol H 2 O)/((11.099 mol H 2 O + 0.300 molsucros))) x 355 Torr = 345.7 Torr 4. This is a more difficult problem than normally seen with Raoult’s Law. Psolv = X solv x P o solv Benzene Toluene Pure 95.1 torr Pure 28.4 torr 1.0 mol 2.0 mol P solv = (1.0/3.0) x 95.1 2/3 x 28.4 = 31.70 vapor pressure = 18.93 vapor pressure 31.70/(31.70 + 18.93) = 0.626 5. E A. Absence of significantly favorable solute-solute interactions is saying the same thing as the presence of significantly unfavorable solute-solute interactions. The presence of significantly unfavorable solute-solute interactions never helps miscibility (i.e., dissolution); if anything, if the solute-solute interaction is so unfavorable, i.e., if the ΔH is dissolution); if anything, if the solute-solute interaction is so unfavorable, i....
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This note was uploaded on 04/05/2008 for the course CHEM 161, 101 taught by Professor Hansell during the Spring '08 term at Rutgers.

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Chapter_12_and_13_Office_Hour_Packet_Answers - Answers to...

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