# UA CHEM 151 - SD1+In-Lab+Worksheet (2 pages)

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## SD1+In-Lab+Worksheet

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- Pages:
- 2
- School:
- University of Arizona
- Course:
- Chem 151 - General Chemistry I

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CHEM 151 SD1 In Lab Worksheet v2 1 1 Skills Development 1 In Lab Worksheet Your TA s name Chris Zerio Your name Amandip Singh Lab section 001 J Your email asingh11 email arizona edu TA 5 p WS 20 p GRADE 25 p All work must be well written and organized If your penmanship is poor you must type all responses If you need to organize your thoughts please use a separate sheet of paper A major objective of this lab course is to develop skills in scientific communication Just having the right answer is not good enough you must communicate clearly and succinctly and use terms and concepts correctly 1 Volume and Mass Data Table 4 p Construct a data table of the volume and mass values that you personally collected That is for the micropipette volume additions and corresponding masses that you recorded build a table The table must be well organized appropriately titled have proper column headings and have the correct sig figs and units for all numerical entries In this exercise you are developing skills in organizing and presenting tabular data This is an important skill for all future lab work Water Density Volume vs Mass V mL M g 0 500 mL 0 499 g 1 00 mL 0 998 g 1 500 mL 1 497 g 2 00 mL 1 994 g 2 500 mL 2 51 g 3 00 mL 3 01 g 2 Determining Density Graphically 4 p Using Excel prepare a mass versus volume plot for the run you performed Properly title the plot and label the axes correctly Include the equation of the linear trend line from Excel The slope of this line is the density of water as determined by you and your technique Paste in the complete plot below or if working on hardcopy carefully draw the complete plot below Remember use the correct sig figs and units on all values You will likely need to adjust the sig figs for the equation of the linear trend line in Excel In this activity you are being guided towards the correct presentation of graphical information for this lab course and most scientific documents water density Volume vs Mass 3 5 3 f x 1 01x 0 01 Mass g 2 5 2 1 5 1 0 5 0 0 0 5 1 1 5 2 2 5 Volume mL SD1 In Lab v2 1 MY 2017 8 15 17 Chem Think Technical Press CBC UofA 3 3 5 CHEM 151 SD1 In Lab Worksheet v2 1 2 3 Analysis of Precision 4 p All of the following must be in full well written sentences Now consider your mass versus volume plot What does this say about your precision The graph tells us that we got precise data because all the points line up on the slope of the graph That represents our experimental value for the density of the water tested In other words for each volume measured we got a corresponding mass which had a similar ratio of m g 4 Percent Error Calculation 4 p The density of pure water at room temperature 20 oC is 0 9982 g mL Given this and your result determine the percent error To do this first symbolically with mathematical symbols not actual values or words state the equation you used to calculate the percent error Define all variables Next give an example calculation in which actual values are plugged in and the results shown Be certain all sig figs and units are correct In this exercise you are learning how to present calculations in a form appropriate to a scientific document You are expected to follow this format in all subsequent lab work without being prompted pTheoretical 0 9982 g mL pexperimental 1 005 g mL E pe pt pt 100 E percent error pe density experimental pt density theoretical E 1 005 g mL 0 9982 g mL 0 9982 g mL 100 E 6812 5 Analysis of Accuracy 4 All of the following must be in full well written sentences Evaluate the accuracy of your micropipette technique Start by stating the density for water you obtained and the accepted or true value Next state the calculated percent error What does this say about your accuracy In the experimentation we found the density of water to be 1 005 g mL while the theoretical or true value is 0 9982 g mL We had a 0 6812 difference in value Since it was a small percent error proves that our findings were very accurate due to the fact that we were under a 5 error margin SD1 In Lab v2 1 MY 2017 8 15 17 Chem Think Technical Press CBC UofA

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