Alum Lab Conclusion Essay

The purpose of this laboratory was to use two different techniques to attempt to identify the melting point and the mole ratio of hydrated water to anhydrous aluminum, potassium, and sulfate of AlKSO4. The hypotheses were: if the alum was put in a capillary tube the melting point of alum will be able to be determined; and the water of hydration in alum crystals will be possible to determine if the alum is heated with a Bunsen burner. Results: Every compound has its own unique sets of chemical properties. Alum crystals are of great purity and are easily prepared. Because of their purity, they are often used in dyeing cloth, where the alum acts as a source of Al+3 ions which are not contaminated. These properties can be determined experimentally and in this experiment as mentioned above, a few properties of alum were being determined. The first test was to identify the melting point of the alum and compare it to the published value that already exists. The melting point of a substance is a property that indicates at what temperature it goes through a state change of solid to liquid. In order to do this, the alum was placed in a water bath and heated. In the second part of the experiment, the alum was analyzed for water of hydration. When an ionic compound is prepared in aqueous solution and isolated by crystallization, water molecules are incorporated into the compound in fixed proportions. The amount of water incorporated is referred to as the water of hydration. This amount cannot be predicted, so it must be determined experimentally. In order to do this, the alum was heated until all the water was driven off. After the completion of the experiment, it was discovered that the results extracted were very close to the expected results. As seen in the data table, the literature melting point and the one obtained in the experiment were only a little more than .5 away from each other which means pretty accurate results were taken away from this experiment. In regards to the second part of the experiment, a way to see precision in the results would have been to do a second heating of the alum in the crucible. Time, however, did not allow for this so if the experiment was to be done again, better results may be obtained by another trial of that part. This experiment overall was a very good example of how certain properties of substances can only be obtained through experiment. It also showed new techniques of determining properties like melting point and water of hydration that could be used in future experiments.