Effect of Temperature on Solubility of a Salt and the Thermodynamic Relationship
Introduction This experiment examined the effects of changing temperature on the amount of solute that would dissolve in a given amount of water. Water solubility is defined as the mass of solute that will dissolve in 100g water at a given temperature. Different quantities of potassium nitrate, KNO3, were dissolved in the same volume of water at a high temperature. As each solution cooled, the temperature was monitored with a Temperature Probe and the precise moment at which crystals started to form was noted. This is the point at which the solution is saturated and contains the maximum amount of solute at that temperature. Each data pair consists of a solubility value (g of solute per 100 g H2O) and a corresponding temperature. A solubility curve was plotted using the T1 calculator. When saturation exists, equilibrium also exists, and there is dynamic equilibrium between the dissolved and undissolved solute, expressed as
LabPro or CBL 2 interface 400-mL beaker
T1 Graphic Calculator 10-mL graduated cylinder
four 20 x 150-mm test tubes 2 utility clamps
hot plate potassium nitrate, KNO3
1. Goggles were worn for this experiment.
2. Four test tubes were labeled 1-4, and into each tube the amounts of solid shown in the table below were measured out:
3. Precisely 5.0 mL distilled water was added to each test tube (assuming 1.0 g/mL for H2O ).
4. The Temperature Probe was plugged into Channel 1 of the LabPro or CBL 2 interface, and the link cable used to connect the T1 Graphic Calculator to the interface.
5. The calculator was turned on and the DATAMATE program
started. The program was cleared and reset.
6. The calculator and interface were set up for the Temperature Probe.
7. The data collection mode was set up for EVENTS WITH ENTRY mode.
8. A 400-mL beaker was filled three-quarters fu...