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