Electroplating
Background:
Electroplating is an economically important process, often used to reduce corrosion or improve the appearance of objects. During electroplating a thin layer of a desirable metal is deposited onto another object.
During electroplating, the object to be plated is attached to the negative post of a power source, causing the object to gain a negative charge. This will attract positive metallic cations from the electrolytic solution, or “bath”, the object is placed in. In our experiment, positive Cu2+ ions from the bath will become attracted to a nail carrying the negative charge. When the Cu2+ reach the nail they will gain electrons and become reduced to form solid copper:
Cu2+(aq) + 2 e- --> Cu(s)
The copper(II) ions removed from the bath must be replenished; this is accomplished at the anode where a solid copper plate undergoes oxidation:
Cu(s) --> Cu2+(aq) + 2e-
Purpose:
To use electroplating to plate copper onto a metal object such as a nail.
Equipment and Materials:
cathode – the metal object to be plated; an iron nail works well. Or try a brass key or a quarter
anode – a copper strip
electrolytic solution – 1.0 M CuSO4
battery or power source
beaker or glass jar
insulated wire leads with alligator clips at both ends
uninsulated copper wire
popsicle sticks or other support that will cross the top of the beaker or jar – used to suspend the item to be plated (optional)
Procedure:
1. The object to be plated must be clean for good results. Prepare by polishing with some steel wool.
2. Use the uninsulated copper wire to suspend the item to be plated (such as the nail) into the empty beaker. Attach one end of a wire lead to the copper wire supporting the nail and the other end to the NEGATIVE post of the battery or power source
3. Place the copper strip, the anode, into the empty beaker. Attach one end of a wire lead to the copper strip and attach the other end to the POSITIVE post of the battery or power source.
4. Carefully pour the CuSO4 solution into the beaker until it is about two-thirds full. If the entire nail is to be plated it must be fully submerged.
5. Allow the reaction to continue for a half-hour or so. Record your observations while electroplating is continuing.
Observations:
The copper first began turning green. We could not see much of a change on the key through the solution. After a little while, the copper was a solid, very pigmented green color. When we took the key out of the solution, it was almost completely covered in copper. It was very shiny. Once we had rinsed and dried the key, it looked almost powdery or chalky. The copper strip was orange when we first took it out of the water, but after we rinsed and dried it, it also looked chalky. The chalky part was very brittle and thin.
Electroplating is an economically important process, often used to reduce corrosion or improve the appearance of objects. During electroplating a thin layer of a desirable metal is deposited onto another object.
During electroplating, the object to be plated is attached to the negative post of a power source, causing the object to gain a negative charge. This will attract positive metallic cations from the electrolytic solution, or “bath”, the object is placed in. In our experiment, positive Cu2+ ions from the bath will become attracted to a nail carrying the negative charge. When the Cu2+ reach the nail they will gain electrons and become reduced to form solid copper:
Cu2+(aq) + 2 e- --> Cu(s)
The copper(II) ions removed from the bath must be replenished; this is accomplished at the anode where a solid copper plate undergoes oxidation:
Cu(s) --> Cu2+(aq) + 2e-
Purpose:
To use electroplating to plate copper onto a metal object such as a nail.
Equipment and Materials:
cathode – the metal object to be plated; an iron nail works well. Or try a brass key or a quarter
anode – a copper strip
electrolytic solution – 1.0 M CuSO4
battery or power source
beaker or glass jar
insulated wire leads with alligator clips at both ends
uninsulated copper wire
popsicle sticks or other support that will cross the top of the beaker or jar – used to suspend the item to be plated (optional)
Procedure:
1. The object to be plated must be clean for good results. Prepare by polishing with some steel wool.
2. Use the uninsulated copper wire to suspend the item to be plated (such as the nail) into the empty beaker. Attach one end of a wire lead to the copper wire supporting the nail and the other end to the NEGATIVE post of the battery or power source
3. Place the copper strip, the anode, into the empty beaker. Attach one end of a wire lead to the copper strip and attach the other end to the POSITIVE post of the battery or power source.
4. Carefully pour the CuSO4 solution into the beaker until it is about two-thirds full. If the entire nail is to be plated it must be fully submerged.
5. Allow the reaction to continue for a half-hour or so. Record your observations while electroplating is continuing.
Observations:
The copper first began turning green. We could not see much of a change on the key through the solution. After a little while, the copper was a solid, very pigmented green color. When we took the key out of the solution, it was almost completely covered in copper. It was very shiny. Once we had rinsed and dried the key, it looked almost powdery or chalky. The copper strip was orange when we first took it out of the water, but after we rinsed and dried it, it also looked chalky. The chalky part was very brittle and thin.
Conclusions and Questions:
1. Write the half-reaction that occurs at the anode of the electrolytic cell. Identify the reaction as either oxidation or reduction.
1. Write the half-reaction that occurs at the anode of the electrolytic cell. Identify the reaction as either oxidation or reduction.
2. Write the half-reaction that occurs at the cathode of the electrolytic cell. Identify the reaction as either oxidation or reduction.
3. Write a descriptive paragraph or two that explains both the flow of copper ions and electrons through the system.
The copper metal is positively charged, and the key is negatively charged. Because the key is negatively charged, the positively charged ions from the copper are attracted to it, and therefore are attached to it. The copper oxidizes, which means that it loses electrons by the element. The key is going through a process called reduction, which means that it is gaining electrons by a substance. If we want the reaction to keep going, the solution that the metal is in and the metal have to be the same. For example, we would need copper metal and copper chloride for it to work. It would not have the same effect if we used zinc metal and copper chloride, because after all of the precipitate from the copper chloride is used to electroplate the key, the zinc would start to electroplate the key.
The copper metal is positively charged, and the key is negatively charged. Because the key is negatively charged, the positively charged ions from the copper are attracted to it, and therefore are attached to it. The copper oxidizes, which means that it loses electrons by the element. The key is going through a process called reduction, which means that it is gaining electrons by a substance. If we want the reaction to keep going, the solution that the metal is in and the metal have to be the same. For example, we would need copper metal and copper chloride for it to work. It would not have the same effect if we used zinc metal and copper chloride, because after all of the precipitate from the copper chloride is used to electroplate the key, the zinc would start to electroplate the key.
