Freezing Point Depression Experiment: The Freezing Point Of P-Xylene

The freezing point of p-xylene was calculated by taking the average calculated Kf of the three trials of the p-xylene and toluene solution. The average of the three trials was computed as 4.56(C/m) as shown in Table 1, however, the theoretical value was slightly lower than calculated, 4.3(C/m). This resulted in a 6.04% error as shown in Equation 5; possible causes of error could have resulted from adding too much solute or too little solvent, then the calculations would have been off given that the solution was not dilute enough. Having too much solvent could be attributed to having a higher Kf than the theoretical value, given that the solute would not have as much impact on the pure substance, p-xylene. This would raise the Kf value, bringing it closer to the solvent’s Kf. Another source of error resulting in the higher Kf could have resulted from contamination of the solvent or solute, given that it could introduce a polar substance or different molecules which would alter the hydrogen bonding. Using the previously calculated Kf, the molar masses of unknown substances A, C, and D were able to be calculated. However, given that the original Kf was slightly larger than the theoretical value, the molar

Given the 6.04% error resulting from Kf, the calculations results were not consistent with what was expected, however, with the theoretical value the results were as predicted. Possible sources of this error could have resulted from combining too much or two little solvent or solute, which would alter the calculated Kf. If this lab were repeated, assuring the measurements of the solute and solvent were accurate would provide more reputable results. Another potential way to receive a more accurate Kf would include more trials to have an average closer to the theoretical