Freezing Point Depression Report

Freezing Point Depression Report Guidelines (40 points)
Introduction (5 points):
 Briefly describe the freezing point depression phenomenon, including the basis for its description as a colligative property. (1 point)
 Explain the significance of molality for specifying solution concentrations. (1 point)
 Describe the experiment, the goals of the experiment, and why it was performed. (3 points)
Experimental Procedure (2 points):
 Write out the experimental procedure in flowing sentences for all parts.
 Do not use bullet points, check marks, 1,2,3, or a,b,c,
 Do not copy from the lab handout (this point applies to all sections of your lab report).
Results (10 pts):
 Show an example of a curve (graph) used to determine freezing point. (2 points)
 Tabulate freezing points, T values, and molalities for each solution studied. (3 points)
 Show a sample calculation using T=mKf, for one of the known alcohols. (2 points)
 Show a sample calculation for determining the molar mass of your “unknown” alcohol. (2 points)
 Report the sample ID (either A, B, or C) of the “unknown” sample your group tested, along with your final assessment of its chemical identify (either 2-propanol, 1-butanol, or ethanol). (1 point)
Discussion (15 points):
 Explain the conceptual/experimental basis for determining molar mass from solution melting point data. (2 points)
 Describe and rationalize the features of a typical freezing curve, and a typical thawing curve (temperature-versus-time curves). (3 points)
 Briefly describe the approach used to create alcohol solutions for freezing point testing. What are the experimental advantages/disadvantages to combining specific masses of liquids, instead of measuring these by volume? (2 points)
 Do any parts of your experiment necessitate a van’t Hoff factor? Why or why not? (1 point)
 For your calculated results: which experimental steps/measurements carry the greatest potential to adversely affect the reliability of your results? Explain your rationale for each potential source of error you mention. (5 points)
 Regarding your “unknown” molar mass determination: to what extent does your experimental value differ from the known molar mass of the chemical substance you believe your group received? (2 points)
Conclusion (3 points):
 Briefly summarize the objective of the experiment. (0.5 point)
 Briefly summarize the results of the experiment. (0.5 point)
 Give a brief interpretation of your results. (1 point)
 Explain what was learned from this experiment. (1 point)
References (2 points):
 Proper formatting
 Must always have at least 1 citation (lab write-up)
Grammar, Spelling, Formatting (3 points):
 Do not use personal pronouns
o You, I, me, her, him, “the group”, “our group”, them, etc.
 Normal font style, 10-12pt. font, regular margins, 1.5-2.0 spacing

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