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Glassware Calibration and Statistical Analysis Name: Karissa Coker Date: January 23, 2024 Unknown #: NA Abstract: The objective of this experiment is to calibrate the glassware we will be using throughout the semester. This is done by obtaining multiple measurements of the exact volume delivered by the volumetric glassware. Then taking the results to calculate the amount of error from each glassware used. Preforming statistical analysis is extremely helpful in determining the accuracy and precision of the data you obtained. You can find the accuracy of the results by looking at the mean, while the precision is found through the standard deviation of the data. 25 mL pipet: 24.97 ( 0.01) 5 mL pipet: 5.25 ( 0.03) 50 mL buret (50 mL): 50.04 ( 0.04) 50 mL (5 mL increment trial 1): 5.02 ( 0.08) 50 mL (5 mL increment trial 2): 5.01 ( 0.06)
Introduction-Background: In scientific experiments, volumetric glassware plays a crucial role in statistical analysis. Each piece of glassware has its unique manufacturing error provided by the company, along with a specified range of tolerance. To ensure accuracy and precision, it is essential to calibrate each glassware item and compare it to the known tolerance error. Accuracy refers to how closely a measured value aligns with the known value, while precision indicates the consistency of values in relation to each other. Both accuracy and precision are crucial for data reliability, as they demonstrate how well the collected data agrees with established values. For instance, when using a buret to measure liquid volume, it is important to record the initial liquid level and ensure that the observer's eye is at the same height as the top of the liquid reading at the meniscus (Harris, 25). The experiment's success is determined by how well the results align with the known tolerance. Different glassware items have varying errors. For example, a 50 mL buret may read 0.1 (±0.05), a 25 mL pipet may read 0.1 (±0.03), and a 5 mL pipet may read 0.01 (±0.01). When using a transferring pipet, it is advised to hold the pipet against the wall for a few extra seconds to allow complete draining, preventing liquid from being drawn back into the pipet (Harris, 25). This precaution ensures accurate readings and minimizes potential errors. In summary, understanding and calibrating glassware for each experiment is crucial to obtaining the most accurate and precise measurements possible, eliminating potential errors and enhancing the reliability of the collected data. Experimental Procedure: Pipet- First always clean the glassware efficiently by running DI water through it 3 times. Before preforming 3 trials of pipetting 25 mL of water, weigh an empty 50 ml beaker and record the weight. Then pipet 25 mL of DI water, reweigh the beaker and record the weight. Empty the beaker and repeat this for a total of 3 trials. The same steps apply when pipetting 5 mL of water into a beaker for 3 trials. Reweigh the beaker and record the weight on your notebook. Buret- You will perform 2 parts of using a 50 mL buret. Part 1 is filling the buret to the nearest 0.01 mL mark. Weigh an empty 50 mL beaker and record weight. Then deliver a total of 50 mL of water all at once. Record the weight of the beaker with 50 mL of water in it. Repeat this for a total of 2 trials.
Table 2: 50 mL buret (50 mL all at once) Average: 50.04 ST. Deviation: 0.04 95% Confidence Interval: 50.0 0.4 %RSD: 40.1% Table 3: Trial 1 of 50 mL buret (5 mL increments) Calibration Curve for Trial 1 of 50 mL buret in increments of 5 mL Average: 5.02 ST. Deviation: 0.08 95% Confidence Interval: 5.02 0.06 %RSD: 1.6%
Table 4: Trial 2 of 50 mL buret (5 mL increments) Graph 2: Calibration Curve for Trial 2 of 50 mL buret in increments of 5 mL Average: 5.01 ST. Deviation: 0.06 95% Confidence Interval: 5.01 0.04 %RSD: 1.1%
Mean of true volume of water delivered = average of all trials divided by total Mean of true volume of water delivered = (24.97312466 + 24.9829668 + 24.9638851)/3 = 24. Standard deviation of true volume of water delivered = √(x1- x)^2+ (x2- x)^2+ (x3- x)^2 /(n-1) Standard deviation of true volume of water delivered = √(24.97312466- 24.97)^2 + (24. -24.97)^2 + (24.9638851- 24.97)^2/(3-1) = 0. Relative standard deviation = (standard deviation/mean)100%* Relative standard deviation = 0.009542436/24.97332552)*100% = 0. Correction = difference in buret reading - true volume of water delivered between intervals Correction = 5 mL - 4.94406847 mL = 0.05 mL Absolute uncertainty = √(e1)^2 + (e2)^ Absolute uncertainty = √(0.07)^2 + (0.05)^2 = 0.086± Relative uncertainty = absolute uncertainty/ true volume of total water delivered Relative uncertainty = 0.070710678 / 10.02924109 = 0.71% T-Test 95% Confidence Interval = 𝑥 ± 𝑡𝑠 / 𝑛 T-Test 95% Confidence Interval = 24.973 ± (4.303) (0.0095)/3 = 24.973± 0. References and Resources: Harris, Daniel C. Quantitative Chemical Analysis, 7th ed.; W H Freeman: S.1., 2007.
