Analysis of Alum - Christina Wong 4th hour AP Chemistry...

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Christina Wong 4 th hour AP Chemistry 9/26/09 Analysis of Alum, AlK(SO 4 ) 2 · 12H 2 O I. Purpose: The main purpose in this lab was to use the alum we had synthesized to carry out tests to see if our alum created was indeed alum. There are three parts in this where we determine melting point, mole ratio of hydrated water to anhydrous aluminum potassium sulfate, and lastly the percent of sulfate in the alum. These will be compared to calculated values of alum to see how close our alum was to the true alum. II. Procedures: Part 1 The first test we had to perform on the alum was to find its melting point and then compare it to the literature value for it. We packed 0.5 g of crushed alum powder in a capillary tube until 0.5 cm of tube was filled. Then we fastened the capillary tube to a thermometer with a small piece of rubber tubing. Using a clamp and rubber stopper we fastened the thermometer to a ring stand and immersed the bottom of the tube and thermometer into a Thiele tube filled with water. We heated the tube with a Bunsen burner until 0.5 cm of the sample was melted. We recorded the melting point in our data table.
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Thiele tube Capillary tube Part 2 We then analyzed it for water of hydration, through placing the alum on a crucible and weighing it. First, we heated the crucible and cover until the crucible was red hot. We then waited for the crucible to cool off and weighed it on an analytical balance. (Record data) Then, we placed 2 g of alum into the crucible and weighed again. We heated this alum until it melts and all bubbling stopped. We removed the crucible and placed it onto the wire gauze. After that, we cooled it to measure the mass of crucible and cover and anhydrous alum. Part 3 Finally, we determined the ratio of moles of H 2 0 to the moles of AlK(SO 4 ) 2 , and compared them to the correct formula values. We used an analytical balance and weighed 1 g of alum into a 250 ml beaker and dissolved in about 50 ml of distilled water. We calculated the volume of 0.2 M Ba(NO 3 ) 2 needed to precipitate sulfate ions in solution and multiply volume by 2, and adding this amount while slowly stirring. Then we heated the solution under boiling for 15 minutes and left the beaker and watch glass cover sit overnight. The next day, we filtered the precipitate through the vacuum filtration apparatus and made sure every particle of precipitate was transferred into filter. We repeated this step several times and let the filter paper dry overnight. After that, we found the mass of the precipitate and calculated the perfect of sulfate in the alum. (Record in data table)
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III. Data Collection:
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This note was uploaded on 12/03/2011 for the course CHEM BIO P 101 taught by Professor Kk during the Spring '11 term at Rochester.

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Analysis of Alum - Christina Wong 4th hour AP Chemistry...

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