Freezing Point Depression
Calculations
For this experiment, the osmolality given by the machine was equal to the molality. 1) Finding the identity of a unknown substance
Molar Mass of Possible unknown substances (g/mol): * Glycine: 75.067 * Glucose: 180.155 * Mannitol: 182.171 * Sucrose: 342.26 * Lactose: 360.312
Results:
Table 1.1: Table showing the results for the osmolality. 200mg of the unknown was dissolved with 10mL of doubly deionized water. A 0.2mL sample was taken and placed in the Osmometer. Trial Number | Osmolality (mOsm/kg H2O) | 1 | 294 | 2 | 291 | 3 | 296 | Average | 293.67 |
Equation used:
Molality= n1000g solvent
Molality= mM1000g solvent
Molality= mM*1000g solvent
Mass of unknown substance:
0.226 g
Mass of solvent:
9.876 g = 9.876 * 10-3 kg
0.29367OsmkgH2O=0.226gM*9.876*10-3kg solvent
0.29367OsmkgH2O=22.88 gM*kgH2O
M=22.880.29367
M=77.91gmol
Based on the molar mass of calculated, the identity of the unknown substance D is Glycine. 2) Finding the concentration of a known solution
Table 1.2: Table used for the preparation of the calibration curve used to find the concentration of alcohol in a wine. 0.2mL of each sample were taken and placed in the Osometer. Ethanol sample (g EtOH/100mL) | Osmolality (mOsm/kg H2O) | 5.117 | 109 | 7.984 | 181 | 11.13 | 242 | 14.01 | 307 | 18.31 | 404 |
Wine tested: Piesporter (White) 9.0% by volume.
Table 1.3: Table showing the results for the osmolality of a sample of wine. 1mL of wine was diluted with 10 mL of water. A 0.2mL sample was taken and put in the osometer. Trial Number | Osmolality (mOsm/kg H2O) | 1 | 204 | 2 | 204 | Average | 204 |
Figure 1.1: Calibration curve for used for the identification of the concentration of ethanol present in a sample of wine. 5 data points were taken at 5.117g EtOH/100mL solvent, 7.984g EtOH/100mL solvent, 11.13g EtOH/100mL solvent, 14.01g EtOH/100mL solvent and 18.31g EtOH/100mL solvent.
Equation for line: y
For this experiment, the osmolality given by the machine was equal to the molality. 1) Finding the identity of a unknown substance
Molar Mass of Possible unknown substances (g/mol): * Glycine: 75.067 * Glucose: 180.155 * Mannitol: 182.171 * Sucrose: 342.26 * Lactose: 360.312
Results:
Table 1.1: Table showing the results for the osmolality. 200mg of the unknown was dissolved with 10mL of doubly deionized water. A 0.2mL sample was taken and placed in the Osmometer. Trial Number | Osmolality (mOsm/kg H2O) | 1 | 294 | 2 | 291 | 3 | 296 | Average | 293.67 |
Equation used:
Molality= n1000g solvent
Molality= mM1000g solvent
Molality= mM*1000g solvent
Mass of unknown substance:
0.226 g
Mass of solvent:
9.876 g = 9.876 * 10-3 kg
0.29367OsmkgH2O=0.226gM*9.876*10-3kg solvent
0.29367OsmkgH2O=22.88 gM*kgH2O
M=22.880.29367
M=77.91gmol
Based on the molar mass of calculated, the identity of the unknown substance D is Glycine. 2) Finding the concentration of a known solution
Table 1.2: Table used for the preparation of the calibration curve used to find the concentration of alcohol in a wine. 0.2mL of each sample were taken and placed in the Osometer. Ethanol sample (g EtOH/100mL) | Osmolality (mOsm/kg H2O) | 5.117 | 109 | 7.984 | 181 | 11.13 | 242 | 14.01 | 307 | 18.31 | 404 |
Wine tested: Piesporter (White) 9.0% by volume.
Table 1.3: Table showing the results for the osmolality of a sample of wine. 1mL of wine was diluted with 10 mL of water. A 0.2mL sample was taken and put in the osometer. Trial Number | Osmolality (mOsm/kg H2O) | 1 | 204 | 2 | 204 | Average | 204 |
Figure 1.1: Calibration curve for used for the identification of the concentration of ethanol present in a sample of wine. 5 data points were taken at 5.117g EtOH/100mL solvent, 7.984g EtOH/100mL solvent, 11.13g EtOH/100mL solvent, 14.01g EtOH/100mL solvent and 18.31g EtOH/100mL solvent.
Equation for line: y
References: Section B02, Tuesday 14:00-17:00 March 13th, 2012