Solutions and Colligative Properties (In Person)

Edit Experiment

VIDEO LINKS:

Lab Experiments (Write protocols and perform experiments based on these):

  1. Freezing Point of Water
  2. Freezing Point Depression with NaCl Solutions
  3. Freezing Point Depression with CaCl2 Solutions
  4. Boiling Point Elevation with CaCl2 Solutions
  5. Boiling Point Elevation with NaCl Solutions
 

The prelab must include Experimental Protocol, Chemical Table and Equipment Table.

The lab report requires all sections (including prelab sections) to be completed in one document.

 

Experimental Protocol

(Analysis) Watch the experiment videos.  Take notes on the protocol.  Stop the video and re-watch as necessary to acquire the details of the procedure.  Write out the protocol for each part of the experiment.  (It can be written in sequential steps.  Complete sentences are not necessary.)  This is the protocol you will follow, so be detailed.

Chemical Table

(Representation) Prepare your chemical table including the materials you will use in the experiment.  Here is a general template that you may use.  
Chemical Name Chemical Formula Molar Mass (g/mol) Hazards reference PPE
Sodium Chloride NaCl 58.5 Skin irritation https://fscimage.fishersci.com/msds/21105.htm  
           
           
 

Equipment Table

(Analysis) Identify the equipment (type AND size) needed for the experiment and include the name and an image of each.  Be sure to describe the equipment, how to use it, and why it is suitable for this use.
Equipment Name Equipment Picture Intended Purpose
 

Data Collection

(Acquiring competencies) Following your detailed protocol based on the videos, perform all the experiments. Record your observations and take pictures of your key steps in the process.  Your observations and images need to be incorporated in your data section and this section should be as detailed as possible as you will use this information to complete your discussion.

Data Processing

  1. (Existing knowledge, research, and views) Define colligative properties. Provide a reference.
  2. (Manipulation) Calculate the molarity of a solution 10.0g NaCl and 10.0g DI water and 40 g ice.
  3. (Manipulation) Calculate the molality of a solution 10.0g NaCl and 10.0g DI water and 40 g ice.
  4. (Manipulation) Calculate the mole fraction of a solution 10.0g NaCl and 10.0g DI water and 40 g ice.
  5. (Manipulation) Calculate the molarity of a solution 10.0g CaCl2 and 10.0g DI water and 40 g ice.
  6. (Manipulation) Calculate the molality of a solution 10.0g CaCl2 and 10.0g DI water. CaCl2 and 40 g ice.
  7. (Manipulation) Calculate the mole fraction of a solution 10.0g CaCl2 and 10.0g DI water and 40 g ice.
  8. (Manipulation and analysis) Fill in the following table (use your collected values):
Solution composition Mass of solute Moles of solute Mass of water Mass of Ice Molality of solution
5.00 g NaCl
7.50 g NaCl
10.00 g NaCl
4.75 g CaCl2
9.50 g CaCl2
 
  1. (Manipulation and analysis) Create a table as follows (assume the values of i to be 2 for NaCl and 3 for CaCl2, respectively):
Solution composition Molality Freezing point ΔTf i Kf based on experiment % error in Kf
5.00 g NaCl 2
7.50 g NaCl 2
10.00 g NaCl 2
4.75 g CaCl2 3
9.50 g CaCl2 3
  1. (Manipulation and analysis) Create a table as follows (assume the values of i to be 2 for NaCl and 3 for CaCl2, respectively):
Solution composition Molality Boiling point ΔTb i Kb based on experiment % error in Kb
5.00 g NaCl 2
7.50 g NaCl 2
10.00 g NaCl 2
4.75 g CaCl2 3
9.50 g CaCl2 3
  1. (Manipulation and analysis) Create a table as follows (assume the value of Kf to be the literature value 1.86 oC/m):
Solution composition Molality Freezing point ΔTf Kf i based on experiment % error in i
5.00 g NaCl 1.86 oC/m
7.50 g NaCl 1.86 oC/m
10.00 g NaCl 1.86 oC/m
4.75 g CaCl2 1.86 oC/m
9.50 g CaCl2 1.86 oC/m
  1. (Manipulation and analysis) Create a table as follows (assume the value of Kb to be the literature value 0.512 oC/m):
Solution composition Molality Boiling point ΔTb Kb i based on experiment % error in i
5.00 g NaCl 0.512 oC/m
7.50 g NaCl 0.512 oC/m
10.00 g NaCl 0.512 oC/m
4.75 g CaCl2 0.512 oC/m
9.50 g CaCl2 0.512 oC/m
  1. (Representation) Using your water and NaCl solution data, plot the ΔTf as a function of the molality.
  2. (Interpretation) Using your graph from #13, calculate the Kf for water. (Hint: try linear regression)
  3. (Representation) Using your water and NaCl solution data, plot the ΔTb as a function of the molality.
  4. (Interpretation) Using your graph from #15, calculate the Kb for water. (Hint: try linear regression)
  5. (Assumptions and Analysis) Fill in the following table using the observations and data from your experiments.
Assumptions made Testing the assumption If assumptions are wrong ...
NaCl does not dissociate in water. Compare the freezing point of the solution with the freezing point of a nonelectrolyte of identical molality. Changes will be apparent.
Distilled water is pure.  The freezing point will be 0.00 °C.
 

Discussion

Write a minimum one-page (12 font, single spaced) discussion on the experiment conducted this week. Address at least one question in each category as fully as possible integrating the collected data, providing explanations for the observed trends, and evaluating whether your original assumptions about the experiment were validated by the results. The assignment will be graded on completeness, clarity of the explanations and the meaningful integration of the collected and calculated data. Correct grammar and appropriate format for the chemical formulae and chemical reactions is expected. You may use the outline included at the end of this document on how to build your essay to address each category.  
  1. (Existing knowledge, research, and views) Define molarity, molality, mass percent and mole fraction. Provide a reference.
  2. (Existing knowledge, research, and views) Define molality. Provide at least one supported argument for why this unit of concentration is more appropriate for this experiment compared to others, such as molarity. Provide a reference.
  3. (Acquiring competencies) Identify the appropriate glassware needed to make molar vs molal solutions and describe the purpose of both.
  4. (Representation) Classify the chemicals used in this experiment as strong, weak or nonelectrolytes and describe what happens to the chemicals when dissolved in water using the appropriate chemical equations. (Hint: your equation may have a single or a double arrow)
  5. (Existing knowledge, research, and views) Define aqueous solutions and describe what kind of solutes can be used to prepare them. (Hint: address both molecular and ionic compounds) Provide a reference.
  6. (Existing knowledge, research, and views) Define the freezing point; and describe the properties of the solvent that will contribute the most to the freezing point. Provide a reference.
  7. (Analysis) Using your collected data as evidence describe the change in the freezing point of water when a solute is added to create an aqueous solution.
  8. (Existing knowledge, research, and views) Define the freezing point constant and describe how its value is found. Provide a reference.
  9. (Analysis) Compare the freezing point depression constant values that were experimentally determined for the CaCl2 and NaCl solutions and provide at least two supported arguments for the difference.
  10. (Analysis) Using your collected data as evidence describe the change in the boiling point of water when a solute is added to create an aqueous solution.
  11. (Analysis) Compare the boiling point elevation constant values that were experimentally determined for the CaCl2 and NaCl solutions and provide at least two supported arguments for the difference.
  12. (Assumptions) Describe at least one assumption that you made when you selected an i value of 2 for salt and an i value of 3 for CaCl2.
  13. (Analysis) Compare the same freezing points and boiling points from your class. Discuss the accuracy and precision of the experiment.
  14. (Existing knowledge, research, and views) If you lived in an area where it snowed, what would be put on the roads and sidewalks to keep people safe? Provide a reference.
  15. (Analysis) Provide a supported argument for why the method for road safety is preferable over NaCl.
  16. (Experiment design) Propose a protocol for testing a different colligative property that is similar to the experiment you just did.