In an electrolytic cell used for electroplating, what is the immediate consequence of disconnecting the external power source?

The correct option is

The electroplating process stops immediately.

Explanation

Electroplating is an application of the chemical effect of electric current (electrolysis). It is a process where a thin layer of metal is deposited onto a conductive surface by passing a direct current through an electrolyte solution. This process takes place in an electrolytic cell, which converts electrical energy into chemical energy to drive a non-spontaneous redox reaction.

Detailed Analysis:

• Dependency on External EMF: In an electrolytic cell, the external power source acts as an electron pump. It forces electrons to flow to the cathode (negative electrode), creating the necessary potential for the reduction of metal ions (cations) from the solution into solid metal.
• Immediate Cessation: When the power source is disconnected, the circuit is broken, and the flow of electrons stops immediately. Since the reduction reaction at the cathode requires a continuous supply of electrons, the chemical reaction halts instantly.
• Analysis of Incorrect Options:
  • The deposition process continues due to residual ions. Incorrect: While ions remain in the solution, they require an electric field to migrate and undergo discharge. Without the external driving force, deposition cannot continue.
  • The direction of ion flow reverses instantly. Incorrect: Disconnecting the source does not inherently cause the current to reverse. While a small back EMF might exist depending on the electrodes, the primary and immediate consequence regarding the process is that it stops, not that it reverses.
  • The electrolyte solution precipitates out. Incorrect: The solubility of the electrolyte is a function of temperature and chemical nature, not the immediate presence of current. Disconnecting the power does not cause the solute to precipitate out.

Key Takeaway:

Electroplating is a non-spontaneous process strictly driven by an external electromotive force (EMF). Removing the power source removes the energy required to sustain the redox reactions, causing the process to stop immediately.