colligative properties freezing point depression

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I attached the graphs, my data and the lab manual below ( thats lab 16 in case to find it in the lab manual)

Title page

  • Name, date, experiment number, experiment title

Objective

  • Write all objectives of this experiment. Use complete sentences.

Introduction

  • Include the following in your introduction. Write in complete sentences with developed paragraphs. Organize so there is a logical flow of ideas.
    • What is a colligative property?
    • What is the van’t Hoff i-factor?
    • What is molality?
    • What is the important equation for freezing point depression that you will use to calculate the molar mass of the unknown?
  • Give a brief introduction about how the objectives will be met. This should include a brief description of the experiment and what chemicals will be used.

Procedure

  • Cite the manual
  • Include any modifications to the procedure. (You will be doing 3 trials instead of 2). You will skip Part II.

Results

  1. Make a graph for each of your runs.
    • You only need to report your 2 best runs for each part (6 graphs total for parts I, II, and III). Graphs from part I should show how you determined the freezing temperature. Graphs from part II and III must show how you determined the final temperature. Make sure the graphs are labeled so that it is clear which graph is which. Give more descriptive titles than “Trial 1, Part 1” or “Part 3, Trial 2” since they require reference to the procedure. The reader should be able to understand what is being shown in the graph by looking at the title, without having to reference the procedure.
    • You can take screen shots of the graphs if you use logger pro. On Windows, you can use the “Snipping Tool” to take a screenshot of the graph.
  2. Organize into a table
    • Part I
      • The individual freezing points from each trial
      • The average freeing point and standard deviation for the pure lauric acid (if you did 3 trials)
      • (remember to use the format straight X with bar on top plus-or-minus straight s to report the mean and standard deviation)
    • Part II (if completed)
      • The individual freezing points from each trial
      • The mass of water used for each run
      • The average Kf and standard deviation for the lauric acid/water solution.
      • (remember to use the format straight X with bar on top plus-or-minus straight s to report the mean and standard deviation.
    • Part III
      • The mass of unknown and lauric acid used for each run
      • The molal concentration of unknown for each run
      • The individual freezing points from each trial
      • The individual molar mass for the unknown, calculated for each run
      • The average molar mass for the unknown and standard deviation for the unknown
      • (remember to use the format straight X with bar on top plus-or-minus straight s to report the mean and standard deviation)
    • For each run in Parts II and III, report the ΔT for each of the trials, but do not average them. It is inappropriate to average the ΔT for Parts II and III since they should be different depending on how much water or unknown was added.
  3. For Part II: Calculate the %error of your experimental Kf value (literature value for lauric acid: Kf = 3.90oC/m)
  4. For Part III: Calculate the %error for your Molar mass, assuming your unknown is benzoic acid (C7H6O2).

Calculations

  • Provide a sample calculation for each type of calculation

Discussion

  • Analyze the data in your table.
    • Does it make sense; did you get the expected results?
      • Discuss whether the experiment shows evidence of a colligative property
      • Discuss the correlation between molal concentration of unknown and freezing point depression
      • Discuss the calculated %error
    • ****Remember to be quantitative in your analysis*****
  • Discuss sources of error
    • If you have significant error, explain plausible sources of error that explain the error in YOUR experiment.
    • If you had no significant error, discuss general sources of error for this experiment.

Conclusion

  • Restate your major results. Be quantitative.

Postlab Questions

  • Answer the Postlab Questions on the preprinted lab manual sheets.

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