Experiment 2: The Size of Molecules & Avogadro’s Number
Name: Julia Bland
Lab Section: Tuesday A.M. (11:30)
TA’s Name: Yuogi
Date: October 15th
Course: CHEM 1001
Abstract:
Avogadro’s number is one of the vital constants in the chemistry world, used in a multitude of experimental and theoretical calculations. This lab endeavours to experimentally measure Avogadro’s number by adding drops of stearic acid into a known area of distilled water, and using this data, calculate the molecules in the monolayer. The experimental value of Avogadro’s number using stearic acid was found to be 8.689 x 1022 with a 0.144 value of range (0.1-10) being within the literature value order of magnitude. Through this experiment an understanding of the complex …show more content…
This lab began by calibrating a Pasteur pipette using hexanes. After adjusting and turning on the spot ventilation, approximately 5 mL of hexanes was measured and placed in a clean and dry test tube. A clean, dry test tube was also placed beside, in which to keep the pipette when it was not in use. The test tube of hexanes was kept stoppered when not in use. The pipette was used to measure exactly 1mL of hexanes into a graduated cylinder, with the pipette being held vertically and the number of drops being counted and recorded. Seven trials were done, with three chosen as the most precise (accurate to 4-5 drops). The pipette was then cleaned, placed back in test tube and excess hexanes disposed of into the hydrocarbon waste. Next a retort stand was set up with an iron ring attached with a watch glass placed on top about thirty centimetres from the lab bench. The watch glass was obtained from the fume hood, with tongs and was rinses with tap water and then distilled water. After being placed, the watch glass was filled to the edges with distilled water, and the diameter measured with a ruler ( 0.1cm). Approximately 3mL of stearic acid was then roughly measured into a new test tube and stoppered when not in use. The concentration of the stearic acid was also recorded. Using the previously calibrated pipette, stearic acid was added to the watch glass of water one drop at a time, keeping the pipette …show more content…
The first is a reasonable assumption because liquid molecules are close together and there is little free space between particles. The second is a reasonable assumption because due to the hydrophobic and hydrophilic nature of the two ends of the stearic acid molecule, it will be vertical in water. When a monolayer is formed, this will make for an approximately rectangular molecule.
Conclusion:
This lab was undertaken to form a greater understanding of, and to calculate an experimental value of Avogadro’s number. The final experimental value calculated for Avogadro’s number was 8.689 x 1022 mol-1 with a order of magnitude ratio of 0.144. This value is within the acceptable range, though it is not exceedingly accurate to the literature value of Avogadro’s number, and is most likely due to human error during the experiment.
References:
Zhou, Y.; Wheaton, S.L. Chemistry 1001 Laboratory Manual; Mount Allison University; Sackville, 2015; Experiment 4,
Name: Julia Bland
Lab Section: Tuesday A.M. (11:30)
TA’s Name: Yuogi
Date: October 15th
Course: CHEM 1001
Abstract:
Avogadro’s number is one of the vital constants in the chemistry world, used in a multitude of experimental and theoretical calculations. This lab endeavours to experimentally measure Avogadro’s number by adding drops of stearic acid into a known area of distilled water, and using this data, calculate the molecules in the monolayer. The experimental value of Avogadro’s number using stearic acid was found to be 8.689 x 1022 with a 0.144 value of range (0.1-10) being within the literature value order of magnitude. Through this experiment an understanding of the complex …show more content…
This lab began by calibrating a Pasteur pipette using hexanes. After adjusting and turning on the spot ventilation, approximately 5 mL of hexanes was measured and placed in a clean and dry test tube. A clean, dry test tube was also placed beside, in which to keep the pipette when it was not in use. The test tube of hexanes was kept stoppered when not in use. The pipette was used to measure exactly 1mL of hexanes into a graduated cylinder, with the pipette being held vertically and the number of drops being counted and recorded. Seven trials were done, with three chosen as the most precise (accurate to 4-5 drops). The pipette was then cleaned, placed back in test tube and excess hexanes disposed of into the hydrocarbon waste. Next a retort stand was set up with an iron ring attached with a watch glass placed on top about thirty centimetres from the lab bench. The watch glass was obtained from the fume hood, with tongs and was rinses with tap water and then distilled water. After being placed, the watch glass was filled to the edges with distilled water, and the diameter measured with a ruler ( 0.1cm). Approximately 3mL of stearic acid was then roughly measured into a new test tube and stoppered when not in use. The concentration of the stearic acid was also recorded. Using the previously calibrated pipette, stearic acid was added to the watch glass of water one drop at a time, keeping the pipette …show more content…
The first is a reasonable assumption because liquid molecules are close together and there is little free space between particles. The second is a reasonable assumption because due to the hydrophobic and hydrophilic nature of the two ends of the stearic acid molecule, it will be vertical in water. When a monolayer is formed, this will make for an approximately rectangular molecule.
Conclusion:
This lab was undertaken to form a greater understanding of, and to calculate an experimental value of Avogadro’s number. The final experimental value calculated for Avogadro’s number was 8.689 x 1022 mol-1 with a order of magnitude ratio of 0.144. This value is within the acceptable range, though it is not exceedingly accurate to the literature value of Avogadro’s number, and is most likely due to human error during the experiment.
References:
Zhou, Y.; Wheaton, S.L. Chemistry 1001 Laboratory Manual; Mount Allison University; Sackville, 2015; Experiment 4,