Colligative Lab

Purpose (put into lab book)

• The purpose of this lab is to examine how adding sodium chloride to water affects the boiling point of the solution.

Hypothesis (answer in a complete sentence in lab book)

• Pure water normally boils at 100^oC. As we increase the amount of sodium chloride in the solution (increase the molality), what do you think will happen to the boiling point of the solution?

Materials (read the procedure below and list at least 2 chemicals and 5 different materials you will need)

Procedure (summarize in lab book)

Part 1: Make the solution

1. First you will need to prepare the solution. Using a balance, measure out the first mass of the sodium chloride and add it to the flask.

2. Measure out 50mL of water using a graduated cylinder and add it to the flask. Swirl the flask until the solute is dissolved

Part 2: Determine the boiling point

1. Place the flask with the solution on the hot plate and set it to 10.

2. Insert temperature probe and hit collect on LoggerPro. This will track the temperature as the solution heats up and then boils. (Remember: when a substance is undergoing a phase change, like boiling, the temperature will stop rising and remain constant - the flat portion of your graph.)

3. Highlight the flat portion of the graph (which represents when it was boiling) and record the mean temperature as it's boiling point.

4. Repeat parts 1 and 2 for each solution.

Data (put into lab book)

If you were absent for this lab, click here to get your data.

Calculations

1. Calculate the molality for all five solutions that were made (the various amounts of sodium chloride that was added).

2. Be sure to show all your work! Make a list and identify the parts of the solution.

Graph (use a piece of graph paper printed from the internet or graph in your lab notebook by hand)

• Graph:

  • x axis - Concentration (m)

  • y axis - Boiling Point (^oC)

• Don't forget to label your axes and title the graph.

Conclusion (put into lab book - your 3 paragraph conclusion)

Paragraph #1 - Purpose and what was done (details!)

Paragraph #2 - Explain what the graph tells you. Was your hypothesis correct?

Paragraph #3 - Errors and how you would fix them.