CHEM 103 EXPERIMENT 8 MOLECULAR MASS BY FREEZING POINT

Experiment 8
Molecular Mass by Freezing Point Depression
Data and Calculations:
Known
Mass of empty test tube 18.235 g
Mass of test tube + BHT 24.251 g
Mass of test tube + BHT + naphthalene* 24.859 g
Mass of BHT 6.016 g
Mass of naphthalene 0.608 g
Unknown
Mass of empty test tube #2 18.689 g
Mass of test tube #2 + BHT 24.844 g
Mass of test tube #2 + BHT + phenyl salicylate* 25.895 g
Mass of BHT 6.155 g
Mass of phenyl salicylate* 1.051 g
* Note: Naphthalene is known, phenyl salicylate is unknown


Temperature Data:
Time (sec) Pure BHT BHT + naphthalene BHT + phenyl salicylate
0 85.0 76.3 90.2
20 80.0 73.8 85.0
40 75.8 70.7 81.8
60 72.0 68.0 77.6
80 69.0 65.6 75.3
100 68.8 62.7 75.8
120 69.0 60.3 68.5
140 68.8 60.2 66.3
160 68.6 60.1 63.5
180 68.4 59.8 61.8
200 68.2 59.4 61.2
220 58.9 61.0
240 58.4 60.8
260 57.7 60.3
300 60.0

Known Solution Calculations:
MW of naphthalene 128.17 g/mol
F.P. Depression 7.3 oC
o
kf of BHT 9.26 C/m

Unknown Solution Calculations:
F.P Depression 7.5
MW of Unknown 210.8 g/mol
Known MW 214.22 g/mol
Percent Error 1.61 %


Unknown Solids List:
Naphthalene 128.17 g/mol