Lab 1 Report - Gregory Chekerdjian

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Purdue University *

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11500

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Chemistry

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Feb 20, 2024

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Lab 1: How Do We Make Accurate and Precise Measurements REPORT FORM Answer the following discussion questions. Support your claim using evidence, i.e. experimental data that supports the claim. Cite specific quantitative results. Connect your evidence to your claim using reasoning that explains why your evidence supports your claim. Reasoning should be based on a scientific rule, law, principle or definition. Question #1. Which calculation or value provides you with an indication of the accuracy of the glassware? Which piece(s)has/have the greater accuracy, the 10.00-mL graduated cylinder, 50.0-mL graduated cylinder, 50.00-mL buret, or 10.00-mL pipet? Provide an example for the calculation or value and explain using your quantitative results. Page 1 of 4 To answer these questions, you will need to calculate the following:  mass of water for all trials,  volume of water for all trials,  mean absolute deviation for each measurement device,  percent error for each trial and  average percent error for each measurement device. Your data and these calculations will make up the quantitative results you will use to support your answers to the report questions. It is recommended that you write out at least one calculation and make note of your calculation results in your laboratory notebook for future reference. Laboratory material is also included in exam content, and these can be useful materials for studying for the exams. The 10ml pipet was the most accurate method as it was the closets to 10 ml and had an average of 9.98ml for all three trials. The three trials were 10.0342, 9.9888 and 9.9427 below I showed the percent error and how the average percent error was 0.34%. Trial 1: | 10.0342 − 10.00 | 10.00 × 100 = 0.34% Trial 2: | 9.9888 − 10.00 | 10.00 × 100 = 0.11% Trial 3: | 9.9 427 − 10.00 | 10.00 × 100 = 0.57 % Average: ( 0.34 + 0.11 + 0.57 ) 3 = 0.34 % The device with the lowest MAD was also the 10ml Pipet which means it was the most precise as seen in the calculations below. Average volume added: 9.9888 + 10 . 0342 + 9.9427 3 = 9.9885 mL MAD = ( | 9.9888 − 9.9885 | + | 10.0342 − 9.9885 | + | 9.9 427 − 9.9885 | ) 3 = 0.0306 .

Question #2. Which calculation or value provides you with an indication of the precision of the glassware? Which piece(s) of glassware has/ have the greatest precision for measuring volume: the 10.00- mL graduated cylinder, 50.0-mL graduated cylinder, 50.00-mL buret or 10.00-mL pipet? Provide an example for the calculation or value and explain using your quantitative results. Question #3. Which piece of glassware would you use if the volume of liquid needed be measured relatively quickly and did not need to be extremely precise? Explain your reasoning. Question #4. Which of these pieces of glassware would be best to deliver a precise volume into a solution but you do not know ahead of time what that volume would be? Explain your reasoning. Page 2 of 4 If I had to repeat this experiment and had to measure relatively quickly, I would use the 10 ml graduated cylinder. The 10ml graduated cylinder was by far the simplest to use because you just pour a little less then 10ml and then add a little more with the medicine dropper. If I had to get the most precise volume, I would have used the 10ml pipet as it was the most accurate. Although it took a little more time to use then the others it paid off as I said in question 1 and we ended up with the lowest percent error.

Question #5. Recalculate the mean absolute deviation of the glassware using the combined data from you and the two other groups. What can you say about the difference in precision between your measurements and the combined measurements of the three groups? Has the precision changed? Explain using your quantitative results. Question #6. Recalculate the percent error of the glassware using the combined data from you and the two other groups. What can you say about the difference in accuracy between your measurements and the combined measurements of the three groups? Has the accuracy changed? Explain using your quantitative results. Page 3 of 4 The Average MAD was better than my teams only which shows that the 10ml pipet was precise. MAD Group 2 = ( | 9.9503 − 9.9445 | + | 9.9378 − 9.9 445 | + | 9.9455 − 9.9445 | ) 3 = 0.0045 MAD Group 3 = ( | 9.93 − 9.9567 | + | 9.98 − 9.9567 | + | 9.96 − 9.9567 | ) 3 = 0.0093 Average MAD = ¿ ( 0.0306 + 0.0045 ( group 2 MAD )+ 0.0093 ( group 3 MAD )) 3 = 0.0148

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Question #7. If you went back in time to repeat the measurement for the Hubble Space Telescope, what measure(s) would you use to ensure the correct thickness of the mirror? Explain your reasoning. Page 4 of 4 Using the other groups data, I got a percent error of 0.38% 0.34 + 0.55 ( group 1 )+ 0.27 ( group 2 ) 3 = 0.38% After calculating the other two groups measurements we can still see how the 10ml pipet was very accurate and its average percent error for all 9 trials was only 0.38% which is very reasonable considering 4 different people worked to get these values. If I could go back in time to repeat the measurements for the Hubble Space Telescope, I would make sure its accurate and precise. I would also double check everything and do several tries and take the average of the three trials.