Shelby Thweatt
Chemistry Lab Report
Mrs. Doree
1st Hour
11.25.08
Solubility of a Salt
* Purpose/ Background
The purpose of this lab was to collect necessary data to construct a solubility curve for potassium nitrate (KNO3) in water. Basically what was done was we dissolved different quantities of salt in a given amount of water at a temperature close to the water’s boiling point. Each solution was observed as it was cooling, and the temperature at which crystallization of the salt occurred was recorded. The start of crystallization indicated that the solution had become saturated. At this temperature, the solution had the maximum quantity of solute that can be dissolved in that amount of solvent. After all the data was collected, it was used to construct a solubility curve graph for KNO3. The curve was constructed by plotting all the points, and then connecting the points together with a line to form a curve.
* Data and Calculations
Test Tube # Grams of Crystallization
KNO3/5.0 mL H2O Temperature (0C)
1 2.0g/5.0 mL 32.8
2 4.0g/5.0 mL 68.8
3 6.0g/ 5.0 mL 77.5
4 8.0g/ 5.0 mL 88.2
Calculations
2.0g/5.0 mL = 40.0g/ 100 mL
2g = X
5mL 100
X= 40
4.0g/5.0 mL = 80.0g/ 100 mL
4g = X
5mL 100
X= 80
6.0g/ 5.0 mL = 120.0g/ 100 mL
6g = X
5mL 100
X= 120
8.0g/ 5.0 mL = 160.0g/ 100 mL
8g = X
5mL 100
X= 160
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* Error Analysis
There are several possibilities as to why the results to this lab were not as accurate as they could have been. For example, one possible reason for error is having an inconsistent hot plate temperature. This would cause the data to change and differ from the data that was collected. In addition, it is possible that there was an error in finding certain measurements, which includes water measurements. This would throw off the curve and other results. Also, there could have been an inconsistent thermometer temperature. That as well would have...