orgo lab
CHEM 2510 Laboratory Report: Recrystallization and Melting Points
Cover Page:
Recrystallization and Melting Points
by
Lab Instructor:
January 28, 2014
Purpose: The purpose of this experiment was to recrystallize a 95% pure sample of benzoic acid contaminated with approximately 5% salicylic acid using two different methods to determine the melting points and discover the impurities of the substance.
Results: After recrystallization of the benzoic acid, the starting and ending masses as well as the melting point ranges were determined. This experiment was conducted twice, following the same steps and guidelines.
% Recovery:
[(.34g)/(.99g)]*100 = 34.34%
Melting Point:
Average MP Start Temperature: (119.3+122.2)/2 = 120.75 °C
Average MP End Temperature: (122.2+126.1)/2 = 124.15 °C
Average MP Range: 120.75 - 124.15 °C
Actual MP of Benzoic Acid: 122.4 °C (Fisher Scientific MSDS #02720: Benzoic Acid)
Discussion:
The results of the experiment show a percent yield of 34.34% for the first trial (Part A), and a percent yield of 84.0% for the second trial (Part B). The methods for both trials were generally the same, so the large difference is attributed to the fact that the beaker broke before the gravity-filtering step in the first trial. The beaker was attempted to be picked up by the beaker tongs, but as the hot solution was being poured into the filter, the beaker slipped out of the beaker tongs and shattered, leaving some of the product unfiltered and thus not accounted for in the final product. Although the methods were generally similar in both steps, the gravity filtration step was skipped over in the second trial, which may have accounted for the missing 16% in trial 2, but may have also accounted for the overall relatively high percent yield for this trial. Luckily, the actual melting point of benzoic acid fit within the recorded average
Cover Page:
Recrystallization and Melting Points
by
Lab Instructor:
January 28, 2014
Purpose: The purpose of this experiment was to recrystallize a 95% pure sample of benzoic acid contaminated with approximately 5% salicylic acid using two different methods to determine the melting points and discover the impurities of the substance.
Results: After recrystallization of the benzoic acid, the starting and ending masses as well as the melting point ranges were determined. This experiment was conducted twice, following the same steps and guidelines.
% Recovery:
[(.34g)/(.99g)]*100 = 34.34%
Melting Point:
Average MP Start Temperature: (119.3+122.2)/2 = 120.75 °C
Average MP End Temperature: (122.2+126.1)/2 = 124.15 °C
Average MP Range: 120.75 - 124.15 °C
Actual MP of Benzoic Acid: 122.4 °C (Fisher Scientific MSDS #02720: Benzoic Acid)
Discussion:
The results of the experiment show a percent yield of 34.34% for the first trial (Part A), and a percent yield of 84.0% for the second trial (Part B). The methods for both trials were generally the same, so the large difference is attributed to the fact that the beaker broke before the gravity-filtering step in the first trial. The beaker was attempted to be picked up by the beaker tongs, but as the hot solution was being poured into the filter, the beaker slipped out of the beaker tongs and shattered, leaving some of the product unfiltered and thus not accounted for in the final product. Although the methods were generally similar in both steps, the gravity filtration step was skipped over in the second trial, which may have accounted for the missing 16% in trial 2, but may have also accounted for the overall relatively high percent yield for this trial. Luckily, the actual melting point of benzoic acid fit within the recorded average
References: Class data from Fisher Scientific MSDS #02720: Benzoic Acid