Inquiry Question Solid Copper, Silver, Gold! Or is it? Exploring electroplating!

Transcription

1 Inquiry Question Solid Copper, Silver, Gold! Or is it? Exploring electroplating! Name: Date: As much as solid precious metals are great to have, not many of us can afford them. Many items we use such as jewelry, statues, cookware, auto parts, trophies, etc are made of a cheap metal or alloy and then coated with a desirable metal to give it a particular finish. Sometimes that finish is for aesthetic purposes sometimes its functional. For example, audio jack plugs are often made with brass (70% copper and 30% zinc). Brass is much more durable than pure copper. However, both copper and zinc oxidize easily which decreases the effective contact of the plug into a guitar, amp or other audio equipment. To counter this corrosion issue, the brass can be coated with nickel. Its more resistant to corrosion than brass. This coating of nickel is made using electroplating. We use this same idea to electroplate silver or gold onto jewelry made of cheaper metals and chromium onto bumpers, car parts, bath and kitchen taps. The basic idea is to take a sample of pure metal as one electrode, the object you want to plate as the other electrode and a solution containing the metal ion. This is an electrolytic process and electricity is applied to left the object get a thin coating of the desired metal. Note: always Page 1 of 6

2 be careful to remember the other units of chemistry and take into account others forms of equilibrium that might be involved in your cell component choices. Instructions Using a pencil, answer the following questions. The lab is marked based on clarity of responses, completeness, neatness, and accuracy. Do your best! Please ensure that any data measured (or recorded) includes the appropriate number of significant digits (only one uncertain digit). This activity is divided into three sections: Core this first section explores only the basic core ideas involved in understanding. Students must demonstrate a sound understand with all of their answers in this section BEFORE attempting the next section. Mastery Your instructor will NOT review this section if the Core section above shows any misconceptions. In this section students will make predictions and apply the concepts and ideas learned above. For complete mastery it is expected that data collection and scientific procedures will be as accurate as possible. All work shown should be clear with any units included. Answers should be rounded off to the correct number of significant figures based on the data collected. Ace Once again, your instructor will only look at this section provided he/she is confident that the above Mastery criteria has been met. In this section students will demonstrate a deeper understanding of the concepts through error analysis, experimental design etc. Physics concepts from other units already covered will often be required here. This Project will be graded according to this Marking Rubric (link). Part 1: Core After reading the intro, this all seems a bit like magic And not necessarily good magic. 1. If your friend had a severe allergy to peanuts and went to buy a gold chain or gold bracelet for their medical alert, why would they not just buy a pure gold one? 2. What advantage could there be to having a gold plated chain instead of a pure gold one? Page 2 of 6

3 3. Write an explaination to your friend about how a gold plated necklace is made: What would you use as a solution: Why did you choose the specifc cation and anion for this solution? What would you use an an anode: What is the half-reaction at the anode: What would you use as a cathode: What is the half reaction at the cathode: 4. Draw the electrolytic cell. Be sure to include: Label the anode & cathode Label the ions in solution Label where the + and terminals attach in the cell Label the direction of the electron flow. Page 3 of 6

4 Part 2: Mastery 1. You have a 3-D printer and have printed up a medallion for your friend who is dressing as Doctor Strange for Comic Con. The printing material is a very durable resin. Will the electroplating process be a good choice for finishing the metallic finish on this medallion? Explain 2. You have another friend who likes to design jewelry. She has used copper to make a pair of earrings. She is concerned that they will oxidize quickly when people wear them due to sweat. After a discussion, you both decide that Nickel plating the earrings may extend the life of the earring and reduce corrosion as someone wears them. You know your teacher has some Nickel (II) Hydroxide and Nickel (II) sulphate in the lab. Which would you choose to be the solution? Explain why? Page 4 of 6

5 Part 3: Ace Copper Plating a Brass House Key NOTE: All experimental activities must be supervised by an adult and approved by your teacher Materials Needed: 1.5V D-size battery A battery holder 2 alligator clip leads (wire with alligator clips on each end) Beaker Copper (II) sulphate Copper electrode (or coil of copper wire) Brass key Pencil or chopstick Safety glasses Lab coat Procedure: NOTE: All experimental activities must be supervised by an adult and approved by your teacher 1. Prepare the copper (II) sulphate solution by dissolving some copper (II) sulphate solid in hot water in the beaker. Add copper (II) sulphate until saturate (no more will dissolve). The solution should be dark blue. Let this cool to room temperature. 2. Before a brass key can be copper plated, any oxidizing or coating must be removed. Clean the key with soap and water or toothpaste and water. Dry with a paper towel. 3. Prepare your copper electrode or coil of copper wire by washing it as above. Be sure to fully rinse and dry it. Page 5 of 6

6 4. Attach one end of lead #1 to the + end of your battery and the other end to your copper electrode or coil of copper wire 5. Attach one end of the lead #2 to the end of your battery and the other end attach the key 6. Carefully suspend the key by the lead into the solution by wrapping the lead around a chopstick on pencil and placing it across the top of the beaker containing the solution. Be careful to not let the alligator clip touch the solution. 7. Place the copper electrode (or copper coil) into the solution. Be careful to ensure the electrode does NOT touch the key and that the alligator clip is NOT in the solution. 8. Leave this circuit running for minutes or until you are happy with the amount of copper on the key. Analysis: 1. Which lead is the anode? 2. Which lead is the cathode? 3. What is the reaction taking place at the anode? 4. What is the reaction taking place at the cathode? 5. How can you tell a reaction has taken place? 6. Prepare a simple report showing your lab setup. Include pictures of the key before and after the plating. Place the key in a ziplock baggie and submit with your lab analysis. (it will be returned) Page 6 of 6