Question

Make a sketch of an electrolysis cell that could be used to electroplate nickel onto other metal surfaces. Label the anode and the cathode and show the reactions that occur at each.

Short answer

To sketch an electrolysis cell for nickel plating: draw two electrodes labeled as anode and cathode, add an electrolyte with nickel ions, connect a power source, and depict the oxidation reaction \(Ni \rightarrow Ni^{2+} + 2e^-\) on the anode and the reduction reaction \(Ni^{2+} + 2e^- \rightarrow Ni\) on the cathode.

Step-by-step solution

Drawing the Basic Sketch

Sketch a simple container to represent the cell where the electrolysis will occur. Inside the container, draw two bars parallel to one another; these bars represent the electrodes. On one side, label one bar as the anode and the other as the cathode.

Adding the Electrolyte

Indicate the presence of an electrolyte within the cell by drawing a wavy line to represent the liquid between the anode and the cathode. The electrolyte should be a solution containing nickel(II) ions, such as nickel sulfate.

Labeling the Electrodes

Label the anode as the positive electrode and the cathode as the negative electrode. A direct current source should be connected with the positive end attached to the anode and the negative end to the cathode.

Illustrating the Reactions

At the anode, write the reaction where nickel metal is oxidized: \(Ni \rightarrow Ni^{2+} + 2e^-\). At the cathode, write the corresponding reduction reaction: \(Ni^{2+} + 2e^- \rightarrow Ni\), indicating nickel ions in the solution being reduced to nickel metal on the surface of the cathode.

Depicting the Direction of Ion Movement

Draw arrows to indicate the direction of movement for ions. Nickel(II) ions should be shown moving towards the cathode, while sulfate ions or other non-reactive ions can be shown loosely in the electrolyte, completing the circuit.

Key concepts

Electroplating Process

Electroplating is a fascinating technique used to coat the surface of an object with a thin layer of a different metal. Through this process, items are not only given an enhanced aesthetic appeal but can also be provided with increased resistance to corrosion, improved hardness, reduced friction, and altered conductivity.

The basic setup includes an electrolysis cell containing a conductive liquid solution known as the electrolyte, which typically contains ions of the metal to be plated. The object to be electroplated acts as the cathode, or negative electrode, while the anode, or positive electrode, is usually made of the plating metal. When a direct current is applied, metal ions from the solution deposit onto the cathode, forming a thin metal coating.

Anode and Cathode Reactions

During electroplating, two simultaneous reactions occur at the different electrodes. At the anode, which is the positive electrode, oxidation takes place, where metal atoms lose electrons and dissolve into the electrolyte as positively charged ions. This process can be represented with a general equation:

\( M \rightarrow M^{n+} + ne^- \)

On the other side, at the cathode, which is the negative electrode, reduction occurs. Here, positively charged metal ions from the electrolyte gain electrons and are deposited as a solid metal layer. The reaction is represented as follows:

\( M^{n+} + ne^- \rightarrow M \)

The object to be plated becomes coated by the metal that is reduced and deposited at the cathode.

Nickel Electrolysis

Nickel electrolysis is a type of electroplating where nickel is the metal used for plating. The electrolyte typically comprises nickel sulfate, which provides nickel(II) ions for the process. As current passes through the cell, nickel ions migrate towards the negatively charged cathode and receive electrons to form solid nickel, adhering to the surface of the object being plated.

The equation at the cathode reflects this:

\(Ni^{2+} + 2e^- \rightarrow Ni\).

Conversely, at the anode, elemental nickel loses electrons and enters the solution as ions, which can be represented with the equation:

\(Ni \rightarrow Ni^{2+} + 2e^-\).

This continuous cycle of nickel dissolving and depositing maintains the concentration of nickel in the electrolyte.

Oxidation-Reduction Reactions

Electroplating is essentially a series of oxidation-reduction (redox) reactions where electrons are transferred between species. Oxidation is the loss of electrons, and reduction is the gain of electrons.

During an electroplating process, the anode experiences oxidation: a metal atom loses electrons and becomes a positively charged ion. Meanwhile, reduction happens at the cathode where metal ions in the electrolyte gain electrons to become solid metal. These reactions are critical because they allow the transfer of metal ions from the anode to the cathode, creating the metallic coating.

Understanding these redox reactions is key for controlling the quality and thickness of the electroplated layer, and for ensuring a successful plating process.