Glassware Postlab

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Jan 9, 2024

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Glassware Accuracy and Precision Postlab This document has 2 pages. Show all of your work for each question. Sources do not need to be cited using any particular format, but be sure to give enough information that someone could find the source if they wanted to (e.g. URL, textbook title, author, and page number). To Submit Your Work: Go to Gradescope. You will be uploading your work, so be sure to save as a .pdf before uploading. Gradescope does not accept .docx files! For Mastery on this assignment, you must Master 10 or more rubric items. Questions have one rubric item unless specified otherwise. Preliminary Data Analysis 1. Replicate and fill in the first 6 columns of this table with the data from your group’s summary. Add as many rows as you need to include all of your group’s data. Trial Number Glassware used Volume Measured (mL) Mass of empty vessel (g) Mass of vessel with liquid (g) Mass of liquid Measured (g) Calculated Volume of liquid (mL) 1 Graduated Cylinder 50.00 84.57 134.00 49.43 49.52 2 Graduated Cylinder 50.00 84.57 133.77 49.20 49.29 3 Graduated Cylinder 50.00 84.57 133.92 49.35 49.44 4 Graduated Cylinder 49.99 84.57 133.71 49.14 49.22 5 Gradated Cylinder 50.00 84.57 133.88 49.31 49.40 1 Beaker 50.00 53.16 102.42 49.26 49.35 2 Beaker 50.00 53.16 100.78 47.62 47.71 3 Beaker 50.00 53.16 101.72 48.56 48.65 4 Beaker 50.02 53.16 99.99 46.83 46.91

5 Beaker 50.00 53.16 100.56 47.40 47.49 1 Volumetric Flask 100.00 71.77 171.27 99.50 99.68 2 Volumetric Flask 100.00 71.77 171.24 99.47 99.65 3 Volumetric Flask 100.00 71.77 171.19 99.42 99.60 4 Volumetric Flask 100.00 71.77 171.18 99.41 99.59 5 Volumetric Flask 100.00 71.77 171.21 99.44 99.62 2. Calculate the volume of liquid for each trial from the mass of the liquid. Show all steps of your work for the first trial. For all other trials, simply report the calculated volumes in your table. (2 rubric items) ????𝑖?? ?? ?𝑎??? 𝑎? 23°𝐶 = 0.9982? ?𝐿 ?????? = ?𝑎?? ????𝑖?? ?????? ????????? ???𝑖???? = 49.43? 0.9982?/?𝐿 = 49.52?𝐿 ?????? ?????? = 49.26? 0.9982?/?𝐿 = 49.35?𝐿 ?????? ????????𝑖? ????? = 99.50? 0.9982?/?𝐿 = 99.98?𝐿

Determining Accuracy 3. Start a new table, as shown below. Add as many rows as you need to include all of your group’s data. For one trial, show all the steps of your work for calculating percent error. For all other trials, simply report the % error values in your table. (2 rubric items) Trial Number Glassware used Volume Measured (mL) Calculated Volume of liquid (mL) % error of this trial 1 Volumetric Flask 100 99.68 0.32% 2 Volumetric Flask 100 99.65 0.35% 3 Volumetric Flask 100 99.60 0.40% 4 Volumetric Flask 100 99.59 0.41% 5 Volumetric Flask 100 99.62 0.38% 1 Graduated Cylinder 50.00 49.52 0.96% 2 Graduated Cylinder 50.00 49.29 1.42% 3 Graduated Cylinder 50.00 49.44 1.12% 4 Graduated Cylinder 49.99 49.22 1.54% 5 Graduated Cylinder 50.00 49.40 1.20% 1 Beaker 50.00 49.35 1.30% 2 Beaker 50.00 47.71 4.58%

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3 Beaker 50.00 48.65 2.70% 4 Beaker 50.02 46.91 6.18% 5 Beaker 50.00 47.49 4.42% % ????? = (100)|??𝑎????? − ?ℎ?????𝑖?𝑎?| ?ℎ?????𝑖?𝑎? % ????? ????????𝑖? ????? = (100)|99.68?𝐿 − 100?𝐿| 100?𝐿 % ????? ????????𝑖? ????? = |99.68?𝐿 − 100?𝐿| ?𝐿 % ????? ????????𝑖? ????? = |−0.32?𝐿| ?𝐿 % ????? ????????𝑖? ????? = 0.32 % ????? ????????? ???𝑖???? = (100)|49.52?𝐿 − 50.00?𝐿| 50.00?𝐿 % ????? ????????? ???𝑖???? = (100)|−0.48?𝐿| 50.00?𝐿 % ????? ????????? ???𝑖???? = 48?𝐿 50.00?𝐿 % ????? ????????? ???𝑖???? = 0.96 % ????? ?????? = (100)|49.35?𝐿 − 50.00?𝐿| 50.00?𝐿 % ????? ?????? = (100)|−0.65?𝐿| 50.00?𝐿 % ????? ?????? = 65?𝐿 50.00?𝐿

% ????? ?????? = 1.30 4. Now fill in this table, again showing all of your work for the first entry. Add enough rows to show all the types of glassware you used. (2 rubric items) Glassware used Average % error for this glassware type Volumetric Flask 0.372% Beaker 3.836% Graduated Cylinder 1.248% ? = ∑ ? 𝑖 ? 𝑖=1 ? Volumetric Flask: ? = 0.32 + 0.35 + 0.40 + 0.41 + 0.38 5 ? = 1.86 5 ? = 0.372 5. Which piece of glassware was most accurate? How did you make that determination?

The volumetric flask was the most accurate piece of glassware. I made that determination by comparing the average percent errors of each piece of glassware. Percent error reflects accuracy, with higher values indicating greater inaccuracy. The volumetric flask had the least average percent error (0.32%), indicating it had the greatest accuracy. Determining Precision 6. Using the last column (Calculated Volume of liquid (mL)) of the table in question 1, determine the standard deviation for each piece of glassware your group used. If you studied more than one volume for a single piece of glassware, e.g. both 10 mL and 20 mL with the graduated cylinder, you’ll need to calculate a separate standard deviation for each volume. For one piece of glassware, show all the steps of your work for calculating standard deviation by hand. For all other pieces, simply report the values in your table. (2 rubric items) Glassware used Nominal Volume Measured (mL) Mean of calculated volumes (mL) Std. Deviation of calculated volumes (mL) Volumetric Flask 100 99.628 0.037013511 Graduated Cylinder 50 49.374 0.119498954 Beaker 50 48.022 0.9714525207 𝑆 ? = √ ∑ (? 𝑖 − ? ) 2 ? 𝑖=1 ? − 1 ? = ∑ ? 𝑖 ? 𝑖=1 ? Volumetric Flask:

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? = 99.68 + 99.65 + 99.60 + 99.59 + 99.62 5 ? = 498.14 5 ? = 99.628 𝑆 ? = √ (99.68 − 99.628) 2 + (99.65 − 99.628) 2 + (99.60 − 99.628) 2 + (99.59 − 99.628) 2 + (99.62 − 99.628) 2 5 − 1 𝑆 ? = √ (0.052) 2 + (0.022) 2 + (−0.028) 2 + (−0.038) 2 + (−0.008) 2 4 𝑆 ? = √ 0.002704 + 0.000484 + 0.000784 + 0.001444 + 0.000064 4 𝑆 ? = √ 0.00548 4 𝑆 ? = 0.037013511 7. Which piece of glassware was most precise? How did you make that determination? a. The most precise piece of glassware was the volumetric flask. I made this determination by comparing the standard deviations for each piece of glassware. Higher standard deviations

indicate worse precision. The volumetric flask had the lowest standard deviation (0.037013511), indicating the highest precision. 8. Sometimes you do work where it is very important to be as accurate and precise as possible. Sometimes you do work where approximate volumes are just fine. Which piece of glassware would you use to measure a volume if approximate amounts were OK? Why? a. If approximate amounts are alright, I would use a beaker. According to the results of our experiment, the beaker was the least precise and the least accurate with a 0.9714525207 standard deviation and a 3.836% error. That works well enough for approximate values, though. Beakers are inexpensive and readily available in a variety of volumes. Unlike a volumetric flask, the same beaker can be used to measure multiple different volumes.