Analysis of Potassium Aluminum Sulfate Lab Activity (ScholAR)

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Aligned with AP Chemistry Lab #2

Perform three tests to determine if the crystals formed in the Stoichiometry in the Synthesis of an Ionic Compound Lab Activity are truly Potassium Aluminum Sulfate 12 Hydrate. Melting point, the most common analytical test for solids, is the first test in this activity. A small sample of material is powdered in a mortar and pestle and placed in a capillary tube attached to thermometer and then placed in heated water bath. The temperature at which the compound melts is recorded and compared to published values. The second test determines the amount of water or hydration present in the sample. Some of the Potassium Aluminum Sulfate 12 hydrate is placed in a crucible and weighed. The crucible is then heated to drive off the water of hydration. Once the crucible is cool it is weighed again and the amount of water lost is determined. The final test determines the percent of sulfate in the compound by dissolving a weighed quantity of Potassium Aluminum Sulfate 12 Hydrate in de-ionized water and precipitating the sulfate with an excess of barium ions. The resultant Barium Sulfate is filtered, dried and weighed. From the mass of Barium Sulfate, the percent su1fate in the initial sample can be calculated. Includes materials for 15 setups.

Chemical Contents:
Potassium Aluminum Sulfate 12 hydrate
Barium Nitrate

Additional materials required:
Capillary tubes
Thermometers
250mL beakers
Crucibles with covers
Funnel and filter paper
Mortars and pestles
Bunsen burners
Ring stands and triangle pipe stems
Analytical balance
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