Alum Lab Essay

877 Words4 Pages
10-29-10 Analysis of Alum Purpose: To determine if the sample crystals are really aluminum potassium sulfate or alum. Materials: alum, beaker, hot plate, thermometer, thermometer clamp, mortar, pestle, capillary tubes, small rubber bands, stirring rob, goggles. Procedure: Determine the melting point: 1. Pulverize with pestle about 2.00 grams of alum. 2. Pack the crushed alum into a capillary tube. 3. Level the bottom of the tube with the bottom of the thermometer and fasten with a small rubber band. 4. Fasten the thermometer to the holder. 5. Submerge the tube half way into the beaker of water that is on the hot plate. Since a beaker is being used, stirring the water consistently is necessary. 6. Record the melting point of alum. The powder will turn into a clear liquid. Determine the percent water in the crystals: 1. Crush about 2.00 grams of alum into an evaporating dish. 2. Place the dish on a hot plate and let heat. 3. Take off the hot plate when the bubbling of the crystals has stopped. 4. Let cool and mass the evaporating dish and alum. 5. Repeat until the mass is consistent. Data and Observations: Measured melting point | 93.0 ̊ C | Real melting point | 92.5 ̊ C | Mass of evaporating dish | 47.01 g | Mass of evaporating dish and crushed alum | 49.13 g | Mass of crushed alum | 2.12 g | Mass after 1st heating | 48.17 g | Mass after 2nd heating | 48.16 g | Mass of water driven off | .97 g | Mass of anhydrous alum | 1.15 g | Moles of H2O | .0539 moles | Moles of AlK(SO4)2 | .0045 moles | Mole ratio; H2O/AlK(SO4)2 | 12.0 | During the heating of the crushed alum in the hot water bath, the alum had liquefied. The boiling point temperature that was determined was 93.0 degrees Celsius. This process had taken a long time, but around 90 degrees
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