FREE ESSAY ON CHEMISTRY LAB

CHEMISTRY LAB

Lab Report
Introduction:
The purpose of this lab was determining the molecular weight of an unknown solid organic
compound by freezing point depression. In order to do so, one has to first, freeze
cyclohxane, by putting it in ice cold water, and see what the constant temperature comes
out as. Then, one has to freeze .4 grams of there unknown, and cyclohexane by doing the
same process and also see what the constant temperature will come out as. After figuring
out your constant temperature, on should then plug their numbers into the equations. 
Procedure:
These equations were given in the lab procedures for experiment number ten Experiments
for General Chemistry at Yavapai College
Pure Impure
temp time temp time
23.8 15 24.2 15
21.8 30 22.3 30
16.7 45 16.4 45
12.4 60 12.1 60
10.2 75 9.9 75
9 90 8.7 90
7.9 105 8 105
7.5 120 7.6 120
7 135 7.5 135
6.7 150 7.3 150
6.4 165 7.1 165
6.4 180 6.9 180
6.4 195 6.7 195
6.4 210 6.5 210
6.4 225 6.5 225
6.4 240 6.5 240
temp time temp time
25.5 15 19.7 15
22.7 30 16.5 30
15.7 45 11.5 45
10.8 60 8.4 60
7.9 75 6.5 75
6.1 90 5.4 90
5 105 4.2 105
4.2 120 3.5 120
3.1 135 3.1 135
2.8 150 2.8 150
2.7 165 2.6 165
2.6 180 2.5 180
2.5 195 2.5 195
2.2 210 2.4 210
2.2 225 2.4 225
2.2 240 2.4 240
Pure Substance Impure Substance
Results and Calculations:
Molality = moles of solute/Kilograms solvent Density = 0.77g/ml
D = Mass/volume
Volume = 25ml
(.77g/ml) = (m/25ml) 19.25/g (1kg/1000g) 4.3 = 20* ml *m
= 19.25g = .01925k M = .215 
(.215M) = (.4012/ mw) / (.01925 kg)
= (.00414M) = (.4012/mw)
= (.4012) / (.00414M) = 96.908mw
Conclusion: 
The results for this experiment turned out as the molecular weight being 96.9. The weight
of unknown originally was 128; therefore the molecular weight that was calculated was
only off by 31.1. The percent error of the whole experiment was 34.3%. The only thing
that could have semi contaminated this experiment was the rust from the stirrer. Other
than that, there is nothing else the experimenter can think of.