Lab 1 - Methods of Measurements - Post-Lab - Online Submission. - Walsh PDF

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Your Name: Sanjay Rao Lab Partner’s Name: Lab Section: Measurement Lab, Wed 5.10pm Post-Lab CHEM 121 Experiment 1: Methods of Measurement Instructions 1) 2)

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Fill out this document completely and submit it on Canvas by the specified due date. Any text that is blue you should replace with your answers. Please keep the text blue so it is easier for me to see what you have typed as I grade it. TYPE all data and answers into the template using 12 point font and Arial font. The only thing that can be handwritten are the calculations if you do not use the equation editor – use pen to hand write any calculation. As you type in this document, the spacing will change. Try to keep responses to a question on the same page as the question, and use page breaks if you need to move a question and answer to a new page. Never split a table if you can help it. If you have to split the table and continue it on the next page, you MUST add in the Column Headers at the top of the table so that a person does not need to turn back a page to see what the data is referring to. Do not separate a question from its answer (again we do not want to turn back a page to see what you are answering) While you may collaborate with your partner (or other students) to answer the questions, you must type up your own responses using your own words. Copying another student’s responses will result in a zero for the lab, and repeated offenses will be subject to the Academic Integrity policy set forth in the Student Code of Conduct! Please delete this Instructions section when you are completing your report, delete the red text, and delete the Density of Water Chart, before you turn in the Post-Lab Report file. Both Part 1 and Part 2 should fit on the first page, with the Discussion starting on page 2. Keep the original formatting of the template – do not change the template of the report.

Part 1: Determining the Accuracy of Your Measuring Tools (4 pts) Temperature of Water (°C): 21.4⁰ C 100 mL Beaker

50 mL Graduated Cylinder

50 mL Volumetric Flask

10 mL Syringe

Mass of Tool (Empty) (g)

62.747

92.527

41.197

8.979

Mass of Tool with Water (g)

109.801

141.737

90.937

19.161

Mass of Water (g)1

47.054

49.210

49.740

10.182

Calculated Volume of Water (mL)2

47.16

49.32

49.85

10.20

Percent Error (%)3

6

1

0.3

2

1 Hint: You know how much the glassware and water weighs and you also know what the glassware weighs without anything in it! 2 Use the Density of Water Chart and dimensional analysis to figure this out! 3 Percent (%) Error Equation (note the absolute value symbols):

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|Calculated Volume of Water ( mL ) – Measured Volume (mL)|

Percent ( % ) Error=

MeasuredVolume (mL)

×100 %

Note: Even though you used a 100 mL beaker for the measurement, you only measured 50 mL of water, so this is the value you want to plug into the equation. Be sure to use the proper sig-figs for the measuring tool used.

Density of Water Chart Temp (°C) 14 15 16 17

Density (g/mL) 0.9993 0.9991 0.9990 0.9988

Temp (°C) 18 19 20 21

Density (g/mL) 0.9986 0.9984 0.9982 0.9980

Temp (°C) 22 23 24 25

Density (g/mL) 0.9978 0.9976 0.9973 0.9971

If you are in between temperatures, like 22.7 oC, choose the density closest to your temperature. I would pick the density of 0.9976 g/mL since it’s the closest to my temperature value.

Part 2: Determining the Density of an Unknown Object (4 pts) Color of Object: Blue Mass of Object (g): 17.517g Trial #

1

2

3

4

Initial Volume (mL)

29.0

27.0

32.0

34.2

Volume After Object Added (mL)

43.9

42.0

47.0

49.5

Volume of Object (mL)

14.9

15.0

15.0

15.3

Average Volume of Object (mL): 15.0ml Density of Object (g/mL): 1.17g/ml Discussion 1)

In Part 1, which piece of the measuring tools would you expect to be the most accurate (just based on your own knowledge and the markings on it)? Which one would you expect to be the least accurate? Briefly explain why! (1 pt.) To my knowledge the most accurate seems the 10 syringe which is well graduated to tenth of ml and easy to read and the least is the 100ml beaker as it has limited graduation marks hard to estimate the volume.

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2)

Which measuring tool was actually the most accurate according to your results? In order to justify your answer, your response should discuss the percent error values from your experiment. (1 pt.) The 50ml volumetric flask happened to be the most accurate in measurement and this can be picked up with percentage error values in which the 50ml volumetric flask has least percentage error value 0.3% as compared to the other tools.

3)

Did the accuracy of the measuring tools in Part 1 match your expectations? Explain your answer! (1 pt.) My expectation was not met as the one that I predicted appeared third, the 10ml syringe with a percentage error of 2%, the 50ml graduated cylinder at 1% and 50ml volumetric flask at 0.3% were much better measuring tools and my prediction for the least was correct the 100 beaker at 6%

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For Part 2, you will not know if your sample density measurement is accurate until this lab is graded, but describe three specific things that may have caused error. Be explicit about whether your calculated density of the object would be too high, too low, or could go either way if this source of error was present. (3 pts)

5) 1. The accuracy of with which I followed the experiment design, there can be unnoticed flaws that can affect the results which is part of a systematic error. We are near to perfection but never 100% so results can be affected. 2. The other type error that may affect the results are the random errors that may have occurred and these errors are unpredictable and occur as chance variations which we have no control over such as using tap water which may contain other ions and minerals dissolved in causing effect on the results. 3. The use of the Measuring cylinder has a percentage error of 1% which can have some influence on the results.

Sample Calculations (6 pts) (since I have the sample calculations included in the Post Lab report pages, you do NOT need to add another calculations page).

Remember to use proper sig-figs and units in your calculations!!! 6)

Mass of Water for the trial using the 100 mL beaker (Part 1). Calculation Option 1: Show your calculation using an equation editor or otherwise clearly type the calculation here so that it is easy to follow. Calculation Option 2: Take a clear and appropriately sized photo / scan of your hand-written calculations and insert them here. Make sure that the image transfers into the document appropriately.

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Calculated Volume of Water for the trial using the 100 mL beaker (Part 1). Calculation Option 1: Show your calculation using an equation editor or otherwise clearly type the calculation here so that it is easy to follow. Last modified 9/11/2018

Calculation Option 2: Take a clear and appropriately sized photo / scan of your hand-written calculations and insert them here. Make sure that the image transfers into the document appropriately. 8)

Percent (%) Error Calculation for the trial using the 100 mL beaker (Part 1). Calculation Option 1: Show your calculation using an equation editor or otherwise clearly type the calculation here so that it is easy to follow. Calculation Option 2: Take a clear and appropriately sized photo / scan of your hand-written calculations and insert them here. Make sure that the image transfers into the document appropriately.

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Volume of Object for Trial 1 (Part 2). Calculation Option 1: Show your calculation using an equation editor or otherwise clearly type the calculation here so that it is easy to follow. Calculation Option 2: Take a clear and appropriately sized photo / scan of your hand-written calculations and insert them here. Make sure that the image transfers into the document appropriately.

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Average Volume of Object (Part 2). Calculation Option 1: Show your calculation using an equation editor or otherwise clearly type the calculation here so that it is easy to follow. Calculation Option 2: Take a clear and appropriately sized photo / scan of your hand-written calculations and insert them here. Make sure that the image transfers into the document appropriately.

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Density of Object (Part 2). Calculation Option 1: Show your calculation using an equation editor or otherwise clearly type the calculation here so that it is easy to follow. Calculation Option 2: Take a clear and appropriately sized photo / scan of your hand-written calculations and insert them here. Make sure that the image transfers into the document appropriately. Insert picture of your original signed data sheet here or your report will receive no credit since you cannot prove that you measured the data. Name your file using the name of the lab and lab day and time (ex. Measurement lab Monday 1230) when you upload the file on the assignment page for the lab. You are going to ace this first lab – read the instructions carefully, include units and chemical names on all numbers, correct sig-figs, and put together the final ONE file in the order that the instructor has asked for the format here. Have a friend, tutor, or instructor look over your report if you have the time to get feedback and correct any mistakes.

Last modified 9/11/2018...