Chemical Reactions of Copper and Percent Recovery

Transcription

1 and Percent Recovery EXPERIMENT 9 Prepared by Edward L. Brown, Lee University To take copper metal through series of chemical reactions that regenerates elemental copper. Students will classify the various reactions, write their net ionic equations and identify the driving force responsible for the reaction. beaker (250 ml) graduated cylinder wire gauze ring clamp ring stand A P P A R A T U S Bunsen burner boiling stones glass stirring rod evaporating dish beaker tongs OBJECTIVE APPARATUS AND CHEMICALS C H E M I C A L S Copper wire in numbered test tube Aluminum foil concentrated Nitric Acid (HNO 3 ) Methanol 3.0 M NaOH Acetone 3.0 M HCl A: Equation 9.9: Addition of Concentrated HNO 3 1. Obtain a clean, 250 ml, graduated beaker from your lab drawer. PROCEDURE 2. Place your name or initials on the beaker. 3. Obtain a piece of copper wire from your instructor and determine the mass of the copper [Data Sheet Q1]. 4. Twist the copper wire into a flat, tight coil (the size of a penny) and place it in the bottom of your beaker. 5. Place your beaker in the hood. 6. Either you or your instructor will place ~ 5 ml of concentrated nitric acid (conc HNO 3 is very CAUSTIC Avoid Contact!! Use gloves!!) in the beaker. The copper metal will be oxidized to copper ions (~5 minutes). The noxious gas, NO 2, is produced in this reaction so the beaker must be kept inside the hood. 7. Record your observations [Data Sheet Q2]. Note the state (s, l, g, aq) of each product you will need to know this to balance the equations online. Equations give the states of the reactants but not the products. Copyright 2005 Chem21 LLC. No part of this work may be reproduced, transcribed, or used in any form by any means graphic, electronic, or mechanical, including, but not limited to, photocopying, recording, taping, Web distribution, or information storage or retrieval systems without the prior written permission of the publisher. For permission to use material from this work, contact us at info@chem21labs.com. Printed in United States of America.

2 8. After the copper wire has disappeared, fill your beaker to the 100 ml mark with distilled water (use the graduations on the beaker to measure the water). 9. Write a balanced net ionic equation [On-Line Report Sheet Q3] and classify the type of reaction this represents [On-Line Report Sheet Q4]. B: Equation 9.10: Addition of NaOH 10. Use a graduated cylinder to add 30 ± 2 ml 3.0 M NaOH to the copper nitrate solution. 11. Record your observations [Data Sheet Q5]. 12. Write a balanced net ionic equation [On-Line Report Sheet Q6] and classify the type of reaction this represents [On-Line Report Sheet Q7]. 13. What is driving force (reason) for the reaction [On-Line Report Sheet Q8]. C: Equation 9.11: Addition of Heat 14. Place the beaker on a wire gauze seated on a ring clamp [Figure 9.1]. Place a few boiling stones in the beaker and stir the solution (constant stirring) with a glass stirring rod as you bring the solution almost to boiling. Leave the stirring rod in the solution to avoid losing material on your lab bench. 15. Near the boiling point, the solution will form a brown / black precipitate and all the blue color will disappear. Remove the heat at this point and allow the solution to cool (5-10 minutes) without stirring. 16. Record your observations [Data Sheet Q9]. 17. Write a balanced net ionic equation [On-Line Report Sheet Q10] and classify the type of reaction this represents [On- Line Report Sheet Q11]. 18. If some of the solid has not settled to the bottom of the beaker during the cooling period, add an additional 2 ml 3.0 Figure 9.1 M NaOH dropwise on top of the floating solid. 19. Decant (pour off) the clear solution with minimal loss of the precipitate. The trick is not to pour a little and then stop; then pour a little more, then stop, etc this will just stir up the solid in the bottom of the beaker. The trick to decantation is to pour slowly and constantly until the solid in the bottom of the beaker is just about to be poured out then, stop decanting! 20. Add 100 ml boiling water (use beaker tongs) to the precipitate in the beaker any non-copper impurities will dissolve in the hot water. Allow the solid to sediment for 5 minutes. Decant the water taking care to minimize loss of the copper-containing solid. What are you removing in this step [On-Line Report Sheet Q12]? D: Equation 9.12: Addition of HCl 21. Use a graduated cylinder to add ml 3 M HCl to the beaker. 22. Record your observations [Data Sheet Q13]. 23. Write a balanced net ionic equation [On-Line Report Sheet Q14] and classify the type of reaction this represents [On-Line Report Sheet Q15]. 24. What is driving force (reason) for the reaction [On-Line Report Sheet Q16]? E: Equation 9.13: Addition of Aluminum Experiment 9 9-2

3 25. Place the beaker containing the CuCl 2 into a larger beaker filled ¾ full with ice and water. 26. After 5 minutes, remove this beaker from the ice bath and add ~ 0.25 g aluminum foil to the beaker. At this point two reactions are occurring in the beaker one between the copper ion and aluminum metal [Equation 9.13] and one between the hydrochloric acid and the aluminum metal [Equation 9.14]. 27. This reaction will take 5-10 minutes. You are ready to move on to the next step when the red precipitate of copper no longer forms on the surface of freshly added aluminum foil and there are no shiny pieces of metal (Al) in the beaker and the solution is no longer blue. If aluminum is still present at the end of the reaction, add more 3.0 M HCl; if solid copper is still forming on fresh Figure 9.2 aluminum foil, add more aluminum foil. Record your observations [Data Sheet Q17]. 28. Write a balanced net ionic equation for the reaction between Al and CuCl 2 [On-Line Report Sheet Q18] and classify the type of reaction this represents [On-Line Report Sheet Q19]. What is driving force (reason) for the reaction between Al and HCl [On- Line Report Sheet Q20]? 29. Write a balanced net ionic equation for the reaction between Al and HCl [On-Line Report Sheet Q21] and classify the type of reaction this represents [On-Line Report Sheet Q22]. What is driving force (reason) for the reaction between Al and HCl [On- Line Report Sheet Q23]? F: Isolation of Copper: 30. Decant most of the liquid above the copper metal into another beaker (leave ~ 20 ml). 31. Transfer this remaining 20 ml and the solid copper to a clean, dry evaporating dish. Decant the liquid from the evaporating dish back into the beaker to aid in transferring all the copper. Repeat as necessary so that all the copper has been transferred to the evaporating dish. Finally, decant the water in your evaporating dish away from the copper metal that has settled. 32. Rinse the copper in the evaporating dish with 5 ml water. Use a stirring rod to break up the clumps of copper. Decant the water. 33. Repeat Step 32 with another 5 ml of water (decant the water). 34. Repeat Step 32 a third time with another 5 ml of water (decant the water). 35. Take your evaporating dish and a small beaker to the lab station where the methanol is located (DO NOT TAKE THE METHANOL OR ACETONE TO YOUR LAB STATION!!). Rinse the copper in the evaporating dish with 5 ml methanol. Use a stirring rod to break up the clumps of copper. Decant the methanol into your beaker and then place it in the methanol waste container before proceeding to Step Acetone is located at the same lab station. Rinse the copper in the evaporating dish with 5 ml acetone. Use a stirring rod to break up the clumps of copper. Decant the acetone into your beaker and place it in the acetone waste container before proceeding to Step At your lab station, place the evaporating dish on the top of a beaker containing ½ inch of boiling water [Figure 9.2]. Allow the heat of the boiling water to remove the 1/2 inch H 2 O Experiment 9 9-3

4 remaining traces of acetone and dry the copper (Take Care Not To Allow The Flame To Come Near The Evaporating Acetone!!! Acetone Is Extremely Flammable!!! If the Acetone does ignite, Do Not Panic the fire will not hurt your product and will go out when all the acetone has evaporated.). You may use a glass stirring rod to break up any clumps of copper, but make sure you don t lose any of your product by setting your stirring rod on the counter. Scrape your stirring rod on the side of the evaporating dish to remove any adhering copper. 38. Remove the heat when the copper appears dry and no longer clumps on your stirring rod. To test for complete evaporation of the acetone, briefly pass the flame from your Bunsen burner over the surface of the copper in the evaporating dish if any residual acetone is present, it will burn briefly and then die out. 39. Use non-rubberized tongs to place your evaporating dish on the lab bench to cool. 40. When the evaporating dish is cool to the touch, WIPE THE OUTSIDE DRY WITH A PAPER TOWEL and take it to the balance area. 41. Tare a piece of weighing paper (0.000 g) and quantitatively transfer the solid copper onto the weighing paper. Record its mass [Data Sheet Q24]. 42. Crease the weighing paper and transfer the product to a small vial. Cap the vial and affix a label containing your name and the mass of the copper 10 POINTS NO VIAL, NO POINTS. 43. Determine the % Recovery [On-Line Report Sheet Q25]. Waste Disposal Any aqueous solutions generated in this lab can be flushed down the sink with plenty of water. Lab Report: Once you have turned in your Instructor Data Sheet, lab attendance will be entered and lab attendees will be permitted to access the online data / calculation submission part of the lab report (click on Lab 9 Chemical Reactions of Copper). Enter your data accurately to avoid penalty. The lab program will take you in order to each calculation. If there is an error, you will be given additional submissions (the number and penalty to be determined by your instructor) to correct your calculation. Post-Lab Questions: The questions for this lab can be found at Do Not Wait Until The Last Minute!!!! Computer Problems and Internet Unavailability Happen, But Deadlines Will Not Be Extended!! On the Internet, complete any Post Lab Questions for Laboratory 9. The computer program will check your answer to see if it is correct. If there is an error, you will be given additional submissions (the number and penalty to be determined by your instructor) to correct your answer. Late Submission: Late submission of the lab data / calculations is permitted with the following penalties: - 10 points for submissions up to 1 day late, - 20 points for submissions up to 2 days late. Experiment 9 9-4

5 Laboratory 9 Student Data Sheet Lab 9 Chemical Reactions of Copper Name: Mass: A: Equation 9.9: Addition of HNO 3 1. Mass of Copper Wire g 2. Observations: Cu (s) + HNO 3 (aq) B. Equation 9.10: Addition of NaOH 5. Observations: Cu(NO 3 ) 2 (aq) + NaOH (aq) C. Equation 9.11: Addition of Heat 9. Observations: Cu(OH) 2 (s) + heat D. Equation 9.12: Addition of HCl 13. Observations: CuO (s) + HCl (aq) E. Equation 9.13: Addition of Aluminum 17. Observations: CuCl 2 (aq) + Al (s) AND Al (s) + HCl (aq) F. Isolation of Copper 24. Mass of Copper g Experiment 9 9-5

6 Laboratory 9 Instructor Data Sheet Name: A: Equation 9.9: Addition of HNO 3 1. Mass of Copper Wire g 2. Observations: Cu (s) + HNO 3 (aq) B. Equation 9.10: Addition of NaOH 5. Observations: Cu(NO 3 ) 2 (aq) + NaOH (aq) C. Equation 9.11: Addition of Heat 9. Observations: Cu(OH) 2 (s) + heat D. Equation 9.12: Addition of HCl 13. Observations: CuO (s) + HCl (aq) E. Equation 9.13: Addition of Aluminum 17. Observations: CuCl 2 (aq) + Al (s) AND Al (s) + HCl (aq) F. Isolation of Copper 24. Mass of Copper g Experiment 9 9-6