Test #1 by S6y49rm


									                                                       Test #2
                                                      CHM 529

Name: _________________________                                                   Friday Oct. 31, 2008

Apply the rules of significant digits to report all final answers.

1. The addition of 100.0 g of a compound to 750.0 g of chloroform (Kf = 30.0 K/molal) lowered the freezing
point by 10.5 K. Find the molar mass of the compound. (4 marks)

2. Calculate the solubilityof anthracene (178.23 g/mol) in benzene (78.12 g/mol;  = 0.879) at 25oC in units of
g/100ml, given that the enthalpy of fusion of anthracene is 28.8 kJ/mol and its m.p is 217oC. (5 marks)

3. Consider the following temperature vs. mole fraction of compound 1 diagram.

a. Label: the boiling points for compounds 1 and 2, the azeotrope, bubble line, dew line and show what the
state(s) of the components are in each area of the diagram. (4 marks)

i) If you started with a solution of x1 = 0.70, draw in the tie lines showing 1 theoretical plate (1 vapourization
then 1 condensation). (2 marks)

ii) Use the diagram and estimate what the vapour composition after would be and then the composition of the
condensed vapour. (After the vapourization and condensation from b part i) (2 marks)

iii) Draw what would happen if you kept fractionally distilling? (2 marks)

c. Repeat b but start with x1 = 0.3. (6 marks)

4a. Describe Raoult’s law in words. (2 marks)

b. For a two component mixture (where component 1 has a higher vapour pressure than component 2) sketch a
p vs. x1 diagram if the system follows Raoult’s law. Show how p1, p2 and ptotal changes as x1 changes. What
does the slope of each line represent? (8 marks)

5. At 90.0oC the vapour pressure of toluene is 53.3 kPa. At 90.0oC the vapour pressure of p-xylene is 20.0 kPa.
If we now had a mixture of the two compounds that boils at 90.0oC and exerts 0.500 atm of pressure, what is the
composition of the mixture and the composition of the vapour produced? (6 marks)


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