It loses mass as copper dissolves into the solution.
Explanation
Electroplating is the process of depositing a layer of a desired metal onto another material by means of electricity. This process utilizes the chemical effect of electric current. In the electroplating of copper, the setup typically consists of a copper sulphate solution as the electrolyte, a pure copper plate as the anode (connected to the positive terminal), and the object to be plated as the cathode (connected to the negative terminal).
Analysis of the Process:
- Reaction at the Positive Terminal (Anode): The copper plate connected to the positive terminal of the battery functions as the anode. At this electrode, oxidation occurs. Copper atoms from the metallic plate lose electrons and dissolve into the solution as copper ions ($Cu^{2+}$). The reaction can be represented as:
$Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-$
As the copper atoms leave the plate to enter the solution, the mass of the copper plate decreases. - Reaction at the Negative Terminal (Cathode): The free copper ions in the solution are attracted to the negative terminal. Here, they gain electrons and deposit as solid copper on the object. This causes the object at the cathode to gain mass.
- Conclusion: The copper plate at the positive terminal dissolves to replenish the copper ions in the electrolyte, resulting in a loss of mass.
Key Takeaway:
In an electrolytic cell used for electroplating, the metal electrode connected to the positive terminal (anode) dissolves into the electrolyte, causing it to lose mass, while the electrode at the negative terminal (cathode) gains mass due to metal deposition.