Chemteacher

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Does Solubility Depend on Temperature?

Lab Setup

Introduction

  • Solubility is defined as the quantity of solute that can completely dissolve in a given amount of solvent.
  • This can be expressed in a variety of ways (and units).
  • In this lab you will investigate whether the temperature of an aqueous solution impacts the amount of solute that can completely dissolve in that solution.

Procedure

  • Set up a 600-mL beaker on an iron ring and wire gauze. Add about 400 mL of tap water. Heat the water using bunsen burner.
  • Get a different beaker ready as a cooling bath and set this aside on your lab bench.
  • Add exactly 10.0 mL of distilled water to a test tube.
  • Mass out a sample of potassium nitrate, KNO3. Transfer the solid to the test tube.
  • Stir the mixture to dissolve as much solute as possible.
  • Connect a PASCO thermometer so that you can measure temperature using the Sparkvue app on your iPad.
  • Carefully insert the thermometer and clamp the test tube in the water that is being heated.
  • Use the thermometer to stir the mixture gently until all of the potassium nitrate has dissolved. The temperature may vary from 10 °C to 85 °C depending on the amount of potassium nitrate in the sample.
  • When all of the potassium nitrate has dissolved, loosen the test-tube clamp from the support stand and raise the tube out of the water bath. Turn off the burner. Re-clamp the tube above and to one side of the beaker. Using the thermometer, stir the solution gently and observe it as it cools. As soon as crystallization begins, note the temperature of the solution. It is easiest to see crystals by looking at the bottom of the test tube where they will collect as soon as they begin to form. You may need to add the test tube to a cooling bath to incite crystallization.
  • After the crystallization temperature has been recorded, put the test tube back into the water bath and briefly warm the solution until all of the crystals have re-dissolved. Repeat the cooling procedure to check the crystallization temperature. The two readings should be within 1 degree of each other. If the two readings do not agree within 1 degree, rewarm the solution in the water bath, cool it, and continue until agreement is obtained.

Lab Notes

  • you should prepare the lab in your newly created “Digital LNB”
  • you will create a class set of data where each lab group contributes to information.
  • the amounts of solute should range from 5 grams to 20 grams
  • try and get as many data points in that range as possible
  • each person will write up the lab in the digital LNB, completing all of the parts of lab report

Information

This entry was posted on 2015-05-12 by in Agenda, SHP-CH and tagged , , .

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