Unit 6 Analysis Of Alum Lab Answers
1) Heading a. Analysis of Alum b. September 8,2010 – September 10,2010 c. Asad Mehmood d. Lab Partner: Alec Drey, Sarah Schrader, Seth Kerrey 2) Purpose e. Research Problem: Is what we have alum? In this lab, we will be analyzing alum by doing three different tests. The first will be to find the melting point, the second to find the amount of water in alum, and the third is to find the percent sulfate. We expect the values to be close to the actual. f. Variables: i. Independent 1. The temperature the hot plate was at 2. The amounts of alum used 3. The temperature heated at 4. The number of times filtered ii. Dependent 5. The time in which the compound melted and the melting point calculated 6. The amount that we get back after the experiment
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7. Growth of particles 8. The amount of particles caught iii. Control 9. Room Temperature 10. Lighting 11. Type of water solutions used 12. Materials stayed constant including weighing machine (Fisher) 3) Materials and Procedure g. Materials iv. Part 1: 13. Alum crystals, capillary tube, water bath, beaker (250mL), rubber band, metric ruler, watch glass, glass tubing, universal clamp, thermometer, hot plate, mortar and pestle, wax paper, balance, safety goggles v. Part 2: 14. Alum Crystals, evaporation dish, ring stand, iron ring, Bunsen burner, wire screen, crucible, crucible tongs, balance, safety goggles vi. Part 3: 15. Alum crystals, deionized water bottle, stirring rod, rubber policeman, graduated cylinders (25mL and 50mL), Hot Plate, Watch Glass, Beaker (250mL), Barium Nitrate, Balance, Drying oven, masking tape, safety goggles h. Procedure vii. The Procedure is also located back in the lab manual. viii. Part 1: 16. For this portion of the lab, take some of the alum you have and then crush it into a fine powder and then using a capillary tube, put about a centimeter of the crushed alum into the capillary tube. Put the capillary tube into a glass tube so that the alum powder can be forced to the bottom of the capillary tube. Now attach the tube to the bottom of a thermometer using a rubber band and put that into a beaker of water that is partially boiling on a hot plate. The capillary tube should not be completely submerged. Then after a while, the alum will melt and you will have a temperature reading. ix. Part 2: 17. So first we will measure out about 2 grams of alum and then put that in the crucible. Put the lid on top of it and then put the crucible on an iron stand over the Bunsen burner with a cold flame for about 7-8 minutes. Then switch the flame to a hot flame and then keep on the stand for an additional 5 minutes with the hot flame. Once the alum is cooled, put the alum in a weighing boat and then measure the weight of the alum. x. Part 3: 18. Now for this part of the lab, first measure out about a gram of alum and then pour that into about 50mL of distilled water and mix until the alum is completely dissolved. Next pour about 35mL of the Barium Sulfate into the mixture and there will be a result of a white precipitate. Next heat on barely boiling on a hot plate for about 15 minutes with an evaporating dish on top of the beaker. Then remove and let it stand overnight. The next day, filter the liquid through a Buchner funnel with 2 filter papers and then allow the filter paper and the particles to dry on an evaporating dish in a drying oven. The next day weigh for the mass of the particles collected on the filter paper. 4) Safety i. There are various safety issues in this lab. First of all we will be working with hot glass and as we know, a hot glass and a cold glass don’t look any different so we need to be cautious there. We are also dealing with Bunsen burners and hot plates which just mean we need to be extra cautious and try to avoid burns and burning partners. 5) Data j. Data Collection: xi. Part 1 19. Two temperatures of alum that were recorded a. 89.8℃ b. 92.8℃ 20. Actual melting point of alum = 92.5℃ 21. Average both of the values and then find the percent error c. 89.8+92.82=91.3℃ d. Percent Error= experimental-theoreticaltheoretical ×100→ 91.3-92.592.5 ×100=1.30% 22. Observations e. While melting the alum, we noticed that it turned into a clear liquid over a period of time. xii. Part 2 23. Data f. Alum used: 2.120g ± .001 g. Final amount with the weigh boat: 3.778g ± .001 h. Weigh Boat: 2.647g ± .001 i. Final Amount of Alum: 3.778-2.647= 1.131g± .001 j. Water driven off: 2.120-1.131= .989g± .001 24. Calculations: k. Moles of the alum after heating: i. 1.131g × 1 mole258.2= .00438= .004 l. Moles of the water ii. .989g × 1 mole18.016= .054896= .055 m. Ratio of moles: iii. .055.004= 12.53 n. We know that there is a 1:12 ratio so find the percent error with 12 being the actual iv. Percent Error= experimental-theoreticaltheoretical ×100→ 12.53-1212 ×100=4.44% 25. Observations o. There were some observations that occurred in this portion of the lab as well. First of all, there was a change in the way the alum looked after the removal of the water. It looked like a smoke ball that is used during the 4th of July. xiii. Part 3 26. Data p. Alum used: 1.000g ± .001 q. Filter paper (2): .639g ± .001 r. Watchglass: 43.740g ± .001 s. Final with Watchglass: 49.450g ± .001 27. Calculations t. Mass of precipitate: 49.450- 43.740g- .639g=5.071g ± .001 u. 5.0711 ×100=507.1% sulfate… 28. Observations v. First of all, when we added the Ba(NO3)2 there was mixture of alum and water had turned all white. After boiling and cooling, there was eventually a solid white precipitate that had formed at the bottom of the 250mL beaker. 6) Conclusion k. Overall the lab was a success with a 1.30% error in the first part and 4.44% error in the second part of the lab. The third portion of the lab I had received a peculiar number which means somewhere, we messed up. In this lab, there were three steps that were performed. The first will be to find the melting point, the second to find the amount of water in alum, and the third is to find the percent sulfate. Based on our percent errors, we can conclude that our processes for the portions of the lab were fine except for the third one where we had an excess amount of precipitate on the filter paper. 7) Evaluation l. The way in which we did the lab was ok but could have been improved especially in part 3. There were some things that also had to be assumed in this lab. First of all we assumed that all of the alum was melted in part 1 of the lab. Also we assumed that any water that needed to be evaporated was evaporated and we finally assumed that we had put the mixture of alum, water, and the Ba(NO3)2 on the hot plate for the right amount of time and at the right temperature. Based on our percent errors, there had to be something wrong that occurred in this lab. First of all, as for the first part of the lab, we could have put too much or too little temperature or solid into the capillary tube and this would affect the melting process and this could have also caused there to be an off temperature which overall affected our average. To fix this we could have just put it at a lower temperature for a nice and efficient melting. Also, we could have reduced any chance of random error in this portion as well if we were to increase the amount of trials performed. As for the second portion of the lab, we could have reduced error by timing ourselves so that we weren’t off by a minute or two when we needed to switch the flame type. This could have been solved with a timer of any sort. As for the third portion of the lab, there was lots of error and that could have resulted. This could have been caused by filtering the first liquid only once. It would have been better to filter it out twice to remove any extra unwanted particles. Also another source of error could have resulted from the second filtration process or the drying oven where other classmates put theirs as well. This error could have been reduced drastically. 8) Discussion m. There are various things that occurred during this lab and they will be explained based on part. xiv. The first part, the alum underwent a physical change as the temperature of the water changed the form the alum was in into a clear liquid. This was necessary in order to find the melting point of alum. xv. The second part was a little different and it was needed to find the amount of liquid that had left the alum. As we know, alum is a hydrate and the Bunsen burner used removed the H2O’s that were inside of the formula of KAl(SO4)2 • 12H2O. This made it an anhydrate because of the loss of water. The alum can once again be hydrated by adding water. xvi. In part three, we were find the percent sulfate that was inside of the alum. Back in the formation of KAl(SO4)2 • 12H2O, we were required to use H2SO4. Now to check that it is alum, we had to find the amount of sulfate in the alum by adding some Ba(NO3)2 and this was required in order to precipitate the sulfate in the compound as the form of Ba(SO4)2. 9) Questions n.
Why must objects be cool before their mass is found on a sensitive balance? xvii. It is important because the rising hot air from objects will affect the reading on the balance. The hot current upward will “lift” the object thus altering the reading. o. Comment on the results of the different test you used to verify that the substance tested was alum. xviii. The various test used to determine that the substance tested was alum were truly necessary for any experiment. The results that I received were very accurate to the actual values which overall means that I can accept the fact that what I have is alum. Even though part 3 was off, the other two tests can solidify that I have alum. p. Explain why it is important to use more than one test to verify your substance. xix. It is very important to use more than one test to verify the substance because lots of substances have very similar characteristics. By looking at a different test each time, we can narrow down the substance to a particular one which in this case is
alum. q. What other tests could be made to verify the composition of alum? xx. You could do various tests involving the acids and bases of alum and test aluminum and such. Since you know that Alum is made from aluminum, then you can look into that. You can also test for various other properties with maybe a flame test to also narrow down the options.
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7. Growth of particles 8. The amount of particles caught iii. Control 9. Room Temperature 10. Lighting 11. Type of water solutions used 12. Materials stayed constant including weighing machine (Fisher) 3) Materials and Procedure g. Materials iv. Part 1: 13. Alum crystals, capillary tube, water bath, beaker (250mL), rubber band, metric ruler, watch glass, glass tubing, universal clamp, thermometer, hot plate, mortar and pestle, wax paper, balance, safety goggles v. Part 2: 14. Alum Crystals, evaporation dish, ring stand, iron ring, Bunsen burner, wire screen, crucible, crucible tongs, balance, safety goggles vi. Part 3: 15. Alum crystals, deionized water bottle, stirring rod, rubber policeman, graduated cylinders (25mL and 50mL), Hot Plate, Watch Glass, Beaker (250mL), Barium Nitrate, Balance, Drying oven, masking tape, safety goggles h. Procedure vii. The Procedure is also located back in the lab manual. viii. Part 1: 16. For this portion of the lab, take some of the alum you have and then crush it into a fine powder and then using a capillary tube, put about a centimeter of the crushed alum into the capillary tube. Put the capillary tube into a glass tube so that the alum powder can be forced to the bottom of the capillary tube. Now attach the tube to the bottom of a thermometer using a rubber band and put that into a beaker of water that is partially boiling on a hot plate. The capillary tube should not be completely submerged. Then after a while, the alum will melt and you will have a temperature reading. ix. Part 2: 17. So first we will measure out about 2 grams of alum and then put that in the crucible. Put the lid on top of it and then put the crucible on an iron stand over the Bunsen burner with a cold flame for about 7-8 minutes. Then switch the flame to a hot flame and then keep on the stand for an additional 5 minutes with the hot flame. Once the alum is cooled, put the alum in a weighing boat and then measure the weight of the alum. x. Part 3: 18. Now for this part of the lab, first measure out about a gram of alum and then pour that into about 50mL of distilled water and mix until the alum is completely dissolved. Next pour about 35mL of the Barium Sulfate into the mixture and there will be a result of a white precipitate. Next heat on barely boiling on a hot plate for about 15 minutes with an evaporating dish on top of the beaker. Then remove and let it stand overnight. The next day, filter the liquid through a Buchner funnel with 2 filter papers and then allow the filter paper and the particles to dry on an evaporating dish in a drying oven. The next day weigh for the mass of the particles collected on the filter paper. 4) Safety i. There are various safety issues in this lab. First of all we will be working with hot glass and as we know, a hot glass and a cold glass don’t look any different so we need to be cautious there. We are also dealing with Bunsen burners and hot plates which just mean we need to be extra cautious and try to avoid burns and burning partners. 5) Data j. Data Collection: xi. Part 1 19. Two temperatures of alum that were recorded a. 89.8℃ b. 92.8℃ 20. Actual melting point of alum = 92.5℃ 21. Average both of the values and then find the percent error c. 89.8+92.82=91.3℃ d. Percent Error= experimental-theoreticaltheoretical ×100→ 91.3-92.592.5 ×100=1.30% 22. Observations e. While melting the alum, we noticed that it turned into a clear liquid over a period of time. xii. Part 2 23. Data f. Alum used: 2.120g ± .001 g. Final amount with the weigh boat: 3.778g ± .001 h. Weigh Boat: 2.647g ± .001 i. Final Amount of Alum: 3.778-2.647= 1.131g± .001 j. Water driven off: 2.120-1.131= .989g± .001 24. Calculations: k. Moles of the alum after heating: i. 1.131g × 1 mole258.2= .00438= .004 l. Moles of the water ii. .989g × 1 mole18.016= .054896= .055 m. Ratio of moles: iii. .055.004= 12.53 n. We know that there is a 1:12 ratio so find the percent error with 12 being the actual iv. Percent Error= experimental-theoreticaltheoretical ×100→ 12.53-1212 ×100=4.44% 25. Observations o. There were some observations that occurred in this portion of the lab as well. First of all, there was a change in the way the alum looked after the removal of the water. It looked like a smoke ball that is used during the 4th of July. xiii. Part 3 26. Data p. Alum used: 1.000g ± .001 q. Filter paper (2): .639g ± .001 r. Watchglass: 43.740g ± .001 s. Final with Watchglass: 49.450g ± .001 27. Calculations t. Mass of precipitate: 49.450- 43.740g- .639g=5.071g ± .001 u. 5.0711 ×100=507.1% sulfate… 28. Observations v. First of all, when we added the Ba(NO3)2 there was mixture of alum and water had turned all white. After boiling and cooling, there was eventually a solid white precipitate that had formed at the bottom of the 250mL beaker. 6) Conclusion k. Overall the lab was a success with a 1.30% error in the first part and 4.44% error in the second part of the lab. The third portion of the lab I had received a peculiar number which means somewhere, we messed up. In this lab, there were three steps that were performed. The first will be to find the melting point, the second to find the amount of water in alum, and the third is to find the percent sulfate. Based on our percent errors, we can conclude that our processes for the portions of the lab were fine except for the third one where we had an excess amount of precipitate on the filter paper. 7) Evaluation l. The way in which we did the lab was ok but could have been improved especially in part 3. There were some things that also had to be assumed in this lab. First of all we assumed that all of the alum was melted in part 1 of the lab. Also we assumed that any water that needed to be evaporated was evaporated and we finally assumed that we had put the mixture of alum, water, and the Ba(NO3)2 on the hot plate for the right amount of time and at the right temperature. Based on our percent errors, there had to be something wrong that occurred in this lab. First of all, as for the first part of the lab, we could have put too much or too little temperature or solid into the capillary tube and this would affect the melting process and this could have also caused there to be an off temperature which overall affected our average. To fix this we could have just put it at a lower temperature for a nice and efficient melting. Also, we could have reduced any chance of random error in this portion as well if we were to increase the amount of trials performed. As for the second portion of the lab, we could have reduced error by timing ourselves so that we weren’t off by a minute or two when we needed to switch the flame type. This could have been solved with a timer of any sort. As for the third portion of the lab, there was lots of error and that could have resulted. This could have been caused by filtering the first liquid only once. It would have been better to filter it out twice to remove any extra unwanted particles. Also another source of error could have resulted from the second filtration process or the drying oven where other classmates put theirs as well. This error could have been reduced drastically. 8) Discussion m. There are various things that occurred during this lab and they will be explained based on part. xiv. The first part, the alum underwent a physical change as the temperature of the water changed the form the alum was in into a clear liquid. This was necessary in order to find the melting point of alum. xv. The second part was a little different and it was needed to find the amount of liquid that had left the alum. As we know, alum is a hydrate and the Bunsen burner used removed the H2O’s that were inside of the formula of KAl(SO4)2 • 12H2O. This made it an anhydrate because of the loss of water. The alum can once again be hydrated by adding water. xvi. In part three, we were find the percent sulfate that was inside of the alum. Back in the formation of KAl(SO4)2 • 12H2O, we were required to use H2SO4. Now to check that it is alum, we had to find the amount of sulfate in the alum by adding some Ba(NO3)2 and this was required in order to precipitate the sulfate in the compound as the form of Ba(SO4)2. 9) Questions n.
Why must objects be cool before their mass is found on a sensitive balance? xvii. It is important because the rising hot air from objects will affect the reading on the balance. The hot current upward will “lift” the object thus altering the reading. o. Comment on the results of the different test you used to verify that the substance tested was alum. xviii. The various test used to determine that the substance tested was alum were truly necessary for any experiment. The results that I received were very accurate to the actual values which overall means that I can accept the fact that what I have is alum. Even though part 3 was off, the other two tests can solidify that I have alum. p. Explain why it is important to use more than one test to verify your substance. xix. It is very important to use more than one test to verify the substance because lots of substances have very similar characteristics. By looking at a different test each time, we can narrow down the substance to a particular one which in this case is
alum. q. What other tests could be made to verify the composition of alum? xx. You could do various tests involving the acids and bases of alum and test aluminum and such. Since you know that Alum is made from aluminum, then you can look into that. You can also test for various other properties with maybe a flame test to also narrow down the options.
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