Biochem Lab Questions

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3a) Calculate the mole fraction of B (XB) in the vapor if a mixture of liquids is 64%A and 36%B.
The vapor pressure of pure A (PA°) is 680 torr and the vapor pressure of pure B (PB°) is 740 torr.
Show calculations and give answer to 2 decimal places.

b) The mole fraction of A (XA) in the vapor of a mixture is 0.54 and the sum of the partial
pressures is 758 torr. Calculate the mole fraction of A (NA) in the liquid if the vapor pressure of
pure A (PA°) is 710 torr. (Hint: Find PA first) Show calculations and give answer to 2 decimal
places (if not reporting as a percentage):

4) What is the character of the vapor after each condensation-vaporization cycle in a fractional
distillation? 

5) What specifically causes the vaporization of the lower boiling liquid on the packing in a
fractional distillation? 

6) While heating a sugar solution, the sugar molecule concentration increases while the water
molecule concentration decreases. Why would this increase the boiling point of the solution? 

7) In vacuum distillation, how you do ensure that the liquid does not boil too suddenly upon
reduction of pressure? 

8) Since boiling stones cannot be used to control the bumping of liquids in vacuum distillation,
other methods are used. What is specifically done with glass wool (one of the implements used to
control bumping) when small quantities of material are being distilled via vacuum distillation?

9) What aspect of water makes water a favorable liuqid for a two phase distillation (steam
distillation) of organic compounds?

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