Grossmont College Determination of Molar Mass by Freezing Point Depression Report

page 1 :

Title page-

Name, date, experiment number, experiment title

page 2:

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.

page 3 :

results –

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 ?T for each of the trials, but do not average them. It is inappropriate to average the ?T for Parts II and III since they should be different depending on how much water or unknown was added.

For Part II: Calculate the %error of your experimental Kf value (literature value for lauric acid: Kf = 3.90oC/m)

For Part III: Calculate the %error for your Molar mass, assuming your unknown is benzoic acid (C7H6O2).

page 4:

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.