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Transcript of Solubility Curve
5/11/12 Procedure Results Solubility Curve Lab Report Materials ammonium chloride(NH4Cl)
beaker, 250 mL
glass stirring rod
graduated cylinder, 10 mL
iron ring 1. Prepare the materials.
Label fours test tubes as follows: 4, 4.5, 5, and 5.5.
Obtain 4.00 g of ammonium chloride, then add it to the test tube labeled "4". Repeat this step for 4.50 g, 4.5 g, 5g, and 5.5 g of ammonium chloride.
Add exactly 10.0 mL of water to each test tube.
Set up a hot-water bath, using a 250 mL beaker.
Place the four test tubes into the hot-water bath. Do not let any water from the beaker get into the test tubes; it is imperative that you not change the concentrations of the solutions. Temperature for the first crystallization of the 5.50 g sample: 74.3 C
Temperature for the second crystallization of the 5.50 g sample: 63.4 C
Temperature for the first crystallization of the 5.00 g sample: 68.9 C
Temperature for the second crystallization of the 5.00 g sample: 63.2 C
Temperature for the first crystallization of the 4.50 g sample: 64.3 C
Temperature for the second crystallization of the 4.50 g sample: 56.4 C
Temperature for the first crystallization of the 4.00 g sample: 57.6 C
Temperature for the second crystallization of the 4.00 g sample: 21.2 C
test tube holder
test tubes, 4
wire gauze The solubility of a solute is defined as the amount of solute that will dissolve in a given amount of solvent to make a saturated solution. The solubility of a substance is not constant- it varies with different conditions such as temperature. Objectives Demonstrate how the solubility of a salt varies with temperature.
Plot the solubility curve of a salt on the basis of observed data. 2. Test the solubility versus temperature.
When the hot-water bath begins to boil, store the solutions to help dissolve the ammonium chloride.(Be sure to rinse and dry your stirring rod before putting it into a different solution.)When the solute in all four tubes has completely dissolved, turn off the burner. The bath will remain hot for some time.
Using a test tube holder, remove test tube 5.5 from the water bath and place it in a test tube rack. Place a thermometer into the test tube and allow the solution to cool. You may periodically stir the solution gently with the thermometer.
Check the temperature at which crystallization occurs. Double-check this temperature by reheating the test tube just enough to dissolve the solute again. Recool the solution. If the temperature for the first and second crystallizations differ by more than a few degrees, carefully repeat the reheating and recooling process.
Repeat steps 2b-c for the solutions containing 5.00, 4.50, and 4.00 gof ammonium chloride. Note: A cold-water bath may be needed to hasten the crytallization of the 4.00g sample. Conclusion The solubility of a solid dissolved in a liquid is often larger when the temperature is higher, but smaller when the temperature is lower. We demonstrated this effect by allowing a hot salt solution to cool and then observing the temperature at which the solid begins to crystallize. Bibliography Chemistry lab manual pg. 71-73