© Professor Kathleen V. Kilway, Department of Chemistry, University of Missouri – Kansas City, 2007
Name
Lab Section
GTA
1.
Station
Crystallization
Post-lab report
Fill out the appropriate sections below. Show all work. All answers are to be typed,
including calculations and correct spelling and grammar is required. All calculations
must be shown for credit and correct significant figures are required.
Results
Amounts and units
Initial weight of salicylic acid
Final weight of salicylic acid
Volume of water used to recrystallize
salicylic acid
Initial weight of benzoic acid
Final weight of benzoic acid
Volume of water used to recrystallize
benzoic acid
Initial weight of phthalic acid
Final weight of phthalic acid
Volume of water used to recrystallize
phthalic acid
Compound you took melting point of for
Part 1
melting point of compound above (°C)
Initial weight of naphthalene
Final weight of naphthalene
Initial weight of biphenyl
Final weight of biphenyl
Compound you took melting point of for
Part 2
melting point of compound above (°C)
Crystallization 1
© Professor Kathleen V. Kilway, Department of Chemistry, University of Missouri – Kansas City, 2007
Complete the following questions and submit with your report.
1. The solubility of phthalic acid in 100 mL of water is given in The Handbook of Chemistry and
Physics as 0.54 g at 14 C and 18 g at 99 C.
a. What volume of water was theoretically required to dissolve your phthalic acid?
b. How much phthalic acid should you have theoretically recovered (you may assume that
ice-bath temperature is 14 ºC)?
c. Calculate the % difference for the volume.
d. Calculate the % difference for the recovered mass.
2. Determine the solubility of benzoic acid at 99 ºC and 14 ºC
3. Determine the solubility of salicylic acid at 99 ºC and 14 ºC
4. What is your percent recovery for
a. naphthalene?
b. biphenyl?
Crystallization 2
© Professor Kathleen V. Kilway, Department of Chemistry, University of Missouri – Kansas City, 2007
5. You are given a mixture of benzoic acid and sand. Write a short procedure to recover pure
benzoic acid.
6. Explain why one would recrystallize a solid from a solvent pair. Explain how it works in terms
of solubilities. What were you observing when your ethanol – water solutions became cloudy?
Crystallization 3