Prietha.Thavakumaran.Experiment1

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2080

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Dec 6, 2023

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SC/CHEM 2080: Analytical Chemistry Experiment 1: Calibration of Equipments Prietha Thavakumaran TA: Lisa Azzarello Date Performed: Thursday, September 21 st , 2023 Due: Friday, October 06, 2023

Abstract Calibration of three different pieces of equipment was conducted to test accuracy and precision. The mean volume of 6 trials from the calibration of the transfer pipette was 24.99541215 mL with a standard deviation of ± 0.026748926 mL. Three trials of the volumetric flask calibration were performed and produced a mean volume of 99.96864813 mL with a standard deviation of ± 0.005637023 mL. Finally, the final calibration process for the burette took place via three trials and produced a mean theoretical volume of 25.07966667 mL with a standard deviation of ± 0.129423079 mL, and a mean correction value of -0.082928583 mL with a standard deviation of ± 0.17554563 mL. Results Table 1. Calibration of Transfer Pipette Trial Empty Bottle Weight (g) Bottle and Water Weight (g) Water Weight (g) Temperature (℃) True Volume (mL) 1* 52.2497 77.1399 24.8902 23 24.9773157 2 52.2497 77.1329 24.8832 23 24.9702912 3 52.2496 77.1813 24.9317 23 25.01896095 4 52.1316 77.0144 24.8828 23 24.9698898 5 52.1316 77.0484 24.9168 23 25.0040088 6 52.1316 77.0763 24.9447 23 25.03200645 Average 24.99541215 Standard Deviation 0.026748926 Six trials were conducted as the true volume seemed to be out of tolerance of the 25mL transfer pipette, however, after further analysis, it was determined that all trials are within tolerance. *Refer to Appendix for sample calculation. Table 2. Calibration of Volumetric Flask Trial Empty Flask Weight (g) Flask and Water Weight (g) Water Weight (g) Temperature (℃) True Volume (mL) 1 63.1806 162.7445 99.5639 25.1 99.9621556 2 63.1807 162.7547 99.574 25.1 99.972296 3 63.181 162.7542 99.5732 25.2 99.9714928 Average 99.96864813 Standard Deviation 0.005637023 Three trials were conducted, and the average was within the tolerance range of the 100 mL volumetric flask.

Three trials were conducted on a 50 mL burette, and the average true volume are not within tolerance. Refer to the Appendix for calculations of theoretical volumes for each trial. Discussion In the experiment, the calibration of three different equipment was conducted. The true volume for each calibration was calculated with the correction for buoyancy and thermal expansion using the value mentioned in Table 2 of the laboratory manual associated with each appropriate temperature. For the calibration of the transfer pipette, six trials were conducted, and the average true volume was 24.995 ± 0.03 mL. As the data suggests, the true volume was within tolerance for all six trials and suggests that this glassware is considered Class A as the uncertainty for a 25 mL transfer pipette is ± 0.03 (York 2023). Furthermore, the calibration of the 100 mL volumetric flask took place in three trials and produced a true volume mean of 99.97 ± 0.006 mL. Since the mean value is within the range of the uncertainty for a 100 mL volumetric flask which is ± 0.008 mL, the glassware is considered Class A (York 2023). Lastly, the calibration of the 50 mL burette took place in three trials and produced a true volume mean of 25.162 ± 0.17 mL and a mean theoretical volume of 25.079 ± 0.129 mL. Table 3. Calibration of Burette Trial Initial Volume (mL) Final Volume (mL) Empty Glass Weight (g) Water Weight (g) Glass and Water Weight (g) Theoretical Volume (mL) True Volume (mL) Correction Volume (mL) Temperature (℃) Cumulative Correction (mL) 1 9.98 34.99 52.1345 24.8766 77.0111 25.01 24.9636681 0.0463319 23 0.0463319 2 9.97 35.199 52.1349 25.1533 77.2882 25.229 25.24133655 -0.01233655 23 0.03399535 3 9.99 34.99 52.135 25.1946 77.3296 25 25.2827811 -0.2827811 23 -0.24878575 Average 77.20963333 25.07966667 25.16259525 -0.082928583 -0.056152833 Standard Deviation 0.173176509 0.129423079 0.173517783 0.17554563 0.166938995

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According to the calculated true volume value, the glassware is non-Class A as the value wasn’t in the tolerance range (York 2023). As the burette calibration indicated the glassware could not be Class A, possible sources of error could be human estimation error as the burette reading could not be perfectly measured to its very point causing an inaccurate reading of the volume dispensed. Furthermore, another source of error could possibly be an instrumental error where the balance read is inaccurate. Appendix Sample Calculation At 23 o C, True volume = (grams of water) x (volume of 1 g of water for 23 o C) = 24.8902 g x 1.0035 mL = 24.9773157 mL = 24.977 mL Theoretical Volume Trial 1 = final volume – initial volume = 34.99 mL – 9.98 mL = 25.01 mL Theoretical Volume Trial 2 = final volume – initial volume = 35.199 mL – 9.97 mL = 25.229 mL Theoretical Volume Trial 3 = final volume – initial volume = 34.99 mL – 9.99 mL = 25 mL

References York University. Analytical Chemistry: Laboratory Manual, 2023.