Procedure Guide for Synthesis Experiment Note: Fill in yellow area on tables, remove all grey text. Lab Section: Name e-mail Role Safety Compound aluminum CAS # 7429-90-5 Potassium hydroxide solution 1310-58-3 hydrogen 1333-74-0 potassium aluminum 12003-63-3 hydroxide (potassium aluminate) Sulfuric acid solution 7664-93-9 aluminum hydroxide 21645-51-2 potassium sulfate 7778-80-5 potassium aluminum sulfate NFPA code and meaning - Potassium aluminum sulfate dodecahydrate Necessary precautions (i.e., labcoat, goggles, gloves, hood, etc.) 7784-24-9 Substance Requiring Precaution - Reason for Precaution and route to exposure Physical Properties Compound Densit y Appearanc e units potassium aluminum hydroxide (potassium aluminate) aluminum hydroxide potassium aluminum sulfate potassium aluminum sulfate dodecahydrat e g/cm n/a Clear amber liquid 2.42 Odarless white solid Solubilit y in cold water Solubilit y in hot water Solubilit y in acetone Meltin g point yes yes C 115 in in 300 195.5 1.757 92 Synthesis 1) The first reaction is: 2 Al(s) + 2 KOH(aq) + 6 H2O(l)  2 KAl(OH)4(aq) + 3 H2 (g) a) Green Principal #2 is atom economy. Calculate the atom economy for this reaction. b) Start with approximately 1 gram Al c) Step 1 d) Step 2 e) How much KOH is required for the first reaction to go to completion? Use twice this amount to ensure that the reaction goes to completion. f) What observations need to be recorded to ensure that the reaction has gone to completion? g) What is the solubility of the product? h) What precautions need to be taken for the reactants and products of this step? i) This reaction is slow; you can increase the rate of the reaction by heating. j) Aluminum cans also have plastic coating on the inside to eliminate any metallic taste and paint on the outside for the label. These materials will remain in the solution after the reaction is complete. What problems could this cause with the experiment? How can you remove these materials? 2) After the solution cools, you may run the second reaction. 2 KAl(OH)4(aq) + H2SO4(aq) 2 Al(OH)3(s) + K2SO4(aq) + 2 H2O(l) a) Green Principal #2 is atom economy. Calculate the atom economy for this reaction. b) Step 1 c) Step 2 Note: • The sulfuric acid must react with any excess KOH remaining in the solution and with the KAl(OH)4 produced in the first step. What is the minimum amount of sulfuric acid required for this step? • The reaction of sulfuric acid and potassium hydroxide is extremely exothermic. Slowly add sulfuric acid. • What observations are required to tell if the reaction has gone to completion in this step? • Use the literature to determine the solubility of aluminum hydroxide in hot and cold water. How will this affect your procedure? 3) The third reaction is 2 Al(OH)3(s) + K2SO4(aq) + 3 H2SO4  2 KAl(SO4)2(aq) + 6 H2O(l) a) Green Principal #2 is atom economy. Calculate the atom economy for this reaction. b) Step 1 c) Step 2 Note: • This reaction is slow and requires heating to speed it up. • Check the solubility of all the reactants and products. • How can you determine when the reaction has gone to completion? 4) The fourth reaction is 2 KAl(SO4)2 (aq) + 24 H2O(l)  2 KAl(SO4)2·12H2O(s) a) Green Principal #2 is atom economy. Calculate the atom economy for this reaction. b) Calculate the theoretical yield of the product assuming you start with 10.0 g aluminum. c) Step 1 d) Step 2 Note: this reaction is to recover your product. To understand the hint, you need to prepare a graph of temperature vs solubility for potassium aluminum sulfate. The data is in the table below. Table 2. Solubility of Potassium Aluminum Sulfate Temp (0C) Solubility (g/100 mL 1 3.9 10 9.5 50 44.1 80 134.5 100 357.5 5) Remove impurities in your product by: a) Step 1 b) Step 2 Note: The product at this point probably has some impurities. What are they? What could you rinse with that would remove the impurities without dissolving your product? Check the physical properties of Potassium aluminum sulfate dodecahydrate in the CRC Handbook of Chemistry and Physics for some ideas. 6) Dispose of Waste. How? What does your experimental procedure need to include to address Green principal #1, Prevention? 7) Let dry in your drawer, then weigh during the next lab period. Determine % yield. 8) With a commercial sample; give details a) Individually determine the melting point range – your instructor will demonstrate the use of the melting point apparatus. Be sure to heat slowly so that you can obtain an accurate melting point range. b) Determine if the commercial sample is soluble in acetone c) Determine if the commercial sample is soluble in hot water d) As a group, determine the density of the commercial sample i) Step 1 (How will you determine the volume?) e) Individually determine the pH of a solution of the commercial sample using litmus paper 9) With your product; give details a) Individually determine the melting point – your instructor will demonstrate the use of the melting point apparatus b) Determine if your product is soluble in acetone c) Determine if your product is soluble in hot water d) Individually determine the density i) Step 1 (How will you determine the volume?) e) Individually determine the pH of a solution of your sample using litmus paper 10) Dispose of product How? What does your experimental procedure need to include to address Green principal #1, Prevention? References Experiment 9: Synthesis of potassium aluminum sulfate dodecahydrate Goals 1. Students will learn about reactions Objectives 1. Students will be able to synthesize a compound 2. Students will be able to recrystallize 3. Students will be able to vacuum filter 4. Students will be able to safely handle chemicals 5. Students will be able to do limiting reagent stoichiometry calculations Introduction In this experiment each student will produce potassium aluminum sulfate dodecahydrate from an aluminum can. You will learn about several different experimental procedures. Equipment: 1. Melting point apparatus 2. Scissors 3. Melting point tubes 4. pH paper 5. Digital thermometer (0.1°C) for melting point apparatus 6. Buchner funnel with vacuum tubing and filter paper 7. Stirring hot plate 8. Universal indicator paper 9. Bucket Reagents: 1. Aluminum cans 2. 1.75 M KOH 3. 12.0 M H2SO4 4. Ice 5. Acetone 6. Sodium bicarbonate Procedure The traditional steps in the synthesis of potassium aluminum sulfate dodecahydrate are given below. Use this information to design your procedure. (From http://www.chem.csustan.edu/archive/alum.htm) 1. 2 Al(s) + 2 KOH(aq) + 6 H2O(l) → 2 KAI(OH)(aq) + 3 H2 (g) 2. 2 KAl(OH)4(aq) + H2SO4(aq) + Al(OH)3(s) + K2SO4(aq) + 2 H2O(1) 3. 2 Al(OH)3(s) + K2SO4(aq) + 3 H2SO4 → 2 KAl(SO4)2(aq) + 6H2O(1) 4. 2 KAI(SO4)2 (aq) + 24 H2O(1) ► 2 KAI(SO4)2-12H2O(s) 1. Each student will start with approximately 1 gram Al and run the following reaction: 2 Al(s) + 2 KOH(aq) + 6 H2O(l) → 2 KAl(OH)4(aq) + 3 H2 (g) a. How much KOH is required for the first reaction to go to completion? Use twice this amount to ensure that the reaction goes to completion. b. What observations need to be recorded to ensure that the reaction has gone to completion? c. What is the solubility of the product? d. What precautions need to be taken for the reactants and products of this step? e. This reaction is slow; you can increase the rate of the reaction by heating. f. Aluminum cans also have plastic coating on the inside to eliminate any metallic taste and paint on the outside for the label. These materials will remain in the solution after the reaction is complete. What problems could this cause with the experiment? How can you remove these materials? 2. After the solution cools, you may run the second reaction. 2 KAl(OH).(aq) + H2SO4(aq) +2 Al(OH)3(s) +K2SO4(aq) + 2 H20(1) a. The sulfuric acid must react with any excess KOH remaining in the solution and with the KAl(OH)4 produced in the first step. What is the minimum amount of sulfuric acid required for this step? Use twice this amount. b. How can you tell if the reaction has gone to completion in this step? c. The reaction of sulfuric acid and potassium hydroxide is extremely exothermic, add slowly d. Use the literature to determine the solubility of aluminum hydroxide in hot and cold water. How will this affect your procedure? 3. The third reaction is 2 Al(OH)3(s) + K2SO4(aq) + 3 H2SO4 (aq) → 2 KAI(SO4)2(aq) + 6 H20(1) a. This reaction is also slow and requires heating to speed it up. b. Check the solubility of all the reactants and products. c. How can you determine when the reaction has gone to completion? d. After the reaction has gone to completion, how can you retrieve your product? 4. The fourth reaction step is a hint. 2 KAl(SO4)2 (aq) + 24 H2O(l) → 2 KAI(SO4)2·12H2O(s) To understand the hint, you need to prepare a graph of temperature vs solubility for potassium aluminum sulfate. The data is in the table below. Table 2. Solubility of Potassium Aluminum Sulfate? Temp ("C) Solubility (g/100 mL 1 3.9 10 9.5 50 44.1 80 134.5 100 357.5 5. The product at this point probably has some impurities. What are they? What could you rinse with that would remove the impurities without dissolving your product? Check the physical properties of potassium aluminum sulfate dodecahydrate in the CRC Handbook of Chemistry and Physics for some ideas. 6. Calculate a theoretical yield for the potassium aluminum sulfate dodecahydrate assuming that you start with 15.0 g of aluminum. 7. Dry potassium aluminum sulfate dodecahydrate in drawer and weigh during the next lab period. 8. Determine the physical properties of commercial potassium aluminum sulfate dodecahydrate a. Individually find the melting point using a melting point apparatus. b. As a group, determine the density (How will you determine the volume of a powder?) c. Individually add to water and determine pH. 9. Determine the physical properties of your product a. Individually find the melting point range using a melting point apparatus. M. Duffy, Solubility of Potassium Aluminum Sulfate. 2014. b. Individually determine the density (How will you determine the volume of a powder?) c. Individually add to water and determine pH. 10. Your procedure should include step-by-step detail for the following: a. Include all balanced chemical equations. b. Information requested on the previous pages. c. Detail on what substances you use, the quantities you use and how you measure them, what glassware you use, etc. d. Numbered references for all external information you use. e. Safety and waste disposal information for all reactants and products. f. Detail should be sufficient for another student to reproduce your experiment using nothing but your procedure.
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