Lab 2_ Glassware Calibrations - Avinash Subramanian

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Subramanian 1 Experiment #3 Lab 3: Acid-Base Titrations Part 1 (Standardization of a NaOH solution) By: Avinash Subramanian CHE 2416, Fall 2022, Section C Laboratory Measurements and Techniques

Subramanian 2 Introduction: The scientific Includes a brief background to introduce the problem or scientific questions, concepts, and challenges that are to be addressed (could include chemical and mathematical equations and the theory). Introduction also provides: o A historical overview on how the selected problem (or problems) has been addressed in the past or are addressed using other approaches (by other groups or people), o Reasons why your proposed approach or method (in this report) is better than other possible approaches to solve the same problem. o An introduction to topics/methods that will be discussed in subsequent sections of your current manuscript or report. Introduction includes details that address abstract’s introductory sentence(s) on problem statement and approach. CITE ALL INFO that refers to past work, supports your claims, or discusses a scientific approach not presented in your paper. All claims that are not strictly based on your own Lab Schedule - Reporting Guidelines CHE2416 Fall 2022.docx Page 4 of 6 data or your own thinking and refer to some other background knowledge, MUST be referenced! The “Introduction” and “Discussion” sections often include the largest number of literature references. Data: Volumetric Flask Calibration Data: Table A

Subramanian 3 Buret Calibration Curve: Figure 1 Buret Calibration Chart: Table B

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Subramanian 4 Pipet Calibration Chart and Graph: Figure 2 Figure 2 continued: Discussion:

Subramanian 5 The primary method for measuring that was used for this lab was observing the mass of volume delivered compared with eye measurement for all of the glassware. Error stemming from the analytical balance should not interfere much with calibration as it would affect all of our data and result in a systematic error that still gives us an accurate calibration. Firstly, the calibration of the 50mL volumetric flask had gone the most smoothly out of our three calibration exercises and its results are depicted in Table A. The mass of the filled flask was 87.0167g which with an empty flask mass of 37.1089 had resulted in a difference of 49.9078g when converted to volume using the density given to us in the lab (0.998207g/mL) had resulted in a volume of 49.9974 mL. This value is within the tolerance level which for 50mL of class A is an error 0.05 mL. A possible source of error that could arise with this calibration would be improper drying of the flask before adding water but as our result was well within the tolerance level I presume that our techniques here were done proficiently. With regards to the calibration of the 50 mL Class B Buret calibration, it was a fairly successful calibration with only one outlier value falling outside of the tolerance level of ± 0.10mL which was a correction value of 0.133008. Two trials were done with the second one being used for calculating the correction values. A likely source of this outlier would be an extra drop of water falling into the Erlenmeyer flask. Another source that could have caused this outlier would be incorrect procedure regarding a possible tilt in the buret while calibrating. Outside of that one outlier, our Class B Buret calibration was done proficiently with all of our correction values being well within the required tolerance level. Calibrating the pipet was done through completing 20 trials of use. The mass of volume technique was utilized here in order to determine the true volume values. This was the hardest calibration for us to complete due to the amount of trials that needed to be done as well as us

Subramanian 6 having little experience with pipetting prior. As Figure 2 shows, our measurements looked to fit two gaussian curves rather than just one curve. The measurements showing this pattern is likely due to having a change in our experimental technique. The gaussian that peaks around segment 8 in Figure 2 is based on data that was collected after we had stopped taking individual empty flask weights for each trial and had used the average of the empty flask weights that were already taken up to that point as shown in Figure 2. All of the measurements for this calibration were taken with some water left over from previous tasks. We had exempted the empty flask weight as it was measured when the flask was dry without water. The Gaussian centered on segment 3 is based on data that was acquired before the method change so we would look to the Gaussian on segment 8 for a more accurate representation of a normal distribution around 25 mL. From this calibration we had determined that either averaging the empty flask weights or more careful pipetting after having to remeasure the flask after each trail had given a more accurate mass delivered. We are not sure which one was responsible for this change in our data but it was likely a combination of the two possibilities. References: 1. Lucy, C.A., Harris, D.C. “Quantitative Chemical Analysis”, W.H. Freeman & Company; New York, 2020. 2. Admin; Ashman, C.; McDermott, P.; Brei, T. M. What is Calibration? https://www.surecontrols.com/why-calibration-of-your-measuring-instruments-is- important/ (accessed Sep 22, 2022).

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Subramanian 7 3. Calibration Facts. https://alevelchemistry.co.uk/definition/calibration/#:~:text=In %20chemistry%2C%20calibration%20is%20defined,measured%20values%20and %20analytical%20quantities. (accessed Sep 22, 2022).