Chapter 13 – Properties of Solutions Colligative Properties (Boiling Point, Freezing Point, Osmotic Pressure Changes) Calculations What is the osmotic pressure of a solution formed by dissolving 25.0 g of aspirin (C9H8O4) in 0.250 L of water at 25 °C? Assume that the volume doesn't change upon the addition of aspirin.
Chem 162-2012 final exam + solutions 4 3 Chem 162-2012 Final Exam + Answers Chapter 14 – Chemical Kinetics Reaction Mechanisms, Activation Energy & Catalysts Calculations A certain enzyme (a biological catalyst) makes a reaction 27 times faster at 36oC. What is the decrease of the activation energy (∆EA) caused by the presence of this enzyme?
Chem 162-2012 final exam + solutions 5 4 Chem 162-2012 Final Exam + Answers Chapter 13 – Properties of Solutions Solution Concentrations Calculations (Molarity, mole fraction, etc.) What is the molality of a 1.562M CaCl 2 solution with a density of 1.203g/cm 3 ? A . 1.517m B. 1.298m C. 1.879m D. 1.562m E. 1.475m 1.562 mol/Lsoln → 1.562 mol/kgsolvent Numerator: OK Denominator 1Lsol’n x (1000 mL/Lsoln) x (1cm 3 /mL) x (1.203g/cm 3 soln) x (1kg/1000gsoln) = 1.203kgsoln gSolute + gSolvent = gSolution MWCaCl 2 = 40.08 + (2 x 35.45) = 110.98g/mol 1.562molCaCl 2 x (110.98g/mol) = 173.35gsolute gsolution - gsolute = gsolvent 1203gsoln – 173.35gsolute = 1030gsolvent = 1.030kgsolvent Combine numerator and denominator: 1.562molCaCl 2 /1.030kgsolvent = 1.517m