Question

What type of reaction takes place at the cathode in a galvanic cell? At the anode?

Short answer

In a galvanic cell, a reduction reaction takes place at the cathode, where metal ions gain electrons to form solid metal deposits. At the anode, an oxidation reaction occurs, in which the solid metal loses electrons and dissolves into the electrolyte solution as its cations.

Step-by-step solution

Understanding Galvanic Cells

A galvanic cell, also known as a voltaic cell, is an electrochemical cell that converts chemical energy into electrical energy through redox reactions. The cell consists of two separate half-cells connected through a salt bridge and an external circuit. Each half-cell contains an electrode (cathode and anode) submerged in an electrolyte solution. In a galvanic cell, a spontaneous redox reaction occurs between the two half-cells, where one substance loses electrons (oxidation) and another substance gains electrons (reduction). The electrons flow from one half-cell to the other through the external circuit, generating an electric current.

Reactions at the Cathode

The cathode is the electrode where the reduction reaction takes place in a galvanic cell. It typically gains a positive charge by accepting electrons from the external circuit. When these electrons are received by the ions in the electrolyte (typically metal cations), they are reduced, which means they gain electrons and form a solid metal deposit on the electrode. This process can be represented by the general reaction: \(M^{n+}(aq) + n e^-(s) \rightarrow M(s)\) Here, M represents a metal ion, and n is the number of electrons accepted during the reduction process.

Reactions at the Anode

The anode is the electrode where the oxidation reaction takes place in a galvanic cell. It typically loses a negative charge by releasing electrons to the external circuit. When these electrons are released, the metal from the electrode (typically a solid metal) dissolves into the electrolyte in the form of its cations. This process can be represented by the general reaction: \(M(s) \rightarrow M^{n+}(aq) + n e^-(s)\) Here, M represents a solid metal, and n is the number of electrons lost during the oxidation process. In summary, the type of reaction taking place at the cathode in a galvanic cell is a reduction reaction, and the type of reaction occurring at the anode is an oxidation reaction.

Key concepts

Oxidation

Oxidation is a term that describes a chemical reaction where a substance loses electrons. In the context of a galvanic cell, oxidation occurs at the anode. This means that the anode undergoes a reaction where its metal atoms lose electrons and become positively charged ions. For example, if we have a metal, M, at the anode, the typical reaction can be written as:

• \(M(s) \rightarrow M^{n+}(aq) + n e^-(s)\)

Here, the metal M in solid form turns into ions \(M^{n+}\) and releases electrons \(n e^-\). These released electrons flow through the external circuit towards the cathode, generating electrical energy along the way. This is a crucial process in a galvanic cell, as it supplies the electrons needed for the overall cell operation.

Reduction

Reduction is the opposite of oxidation. It occurs when a substance gains electrons. In a galvanic cell, this process takes place at the cathode. During this reaction, ions in the electrolyte gain electrons and are transformed back into solid metal. The reduction process at the cathode is what allows the cell to generate a continuous flow of current.

• The general reduction reaction can be expressed as:\(M^{n+}(aq) + n e^-(s) \rightarrow M(s)\)

In this equation, \(M^{n+}\) represents the metal ions in the solution, which are reduced by gaining electrons. This forms a solid metal deposit at the cathode. The reduction process is a necessary component of redox reactions, which are pivotal in the functionality of galvanic cells.

Electrochemical Cell

An electrochemical cell is a device that converts chemical energy into electrical energy through chemical reactions known as redox reactions. Galvanic cells are a type of electrochemical cell that operates spontaneously, producing electric current as a result of electron transfer between electrodes.

• The key features include:
• A pair of electrodes: a cathode and an anode.
• An electrolyte solution in which the electrodes are submerged.
• A salt bridge that maintains charge balance by allowing ions to flow between the two half-cells.
• An external circuit for electron flow.

In a galvanic cell, the spontaneous reaction involves oxidation at the anode and reduction at the cathode. Electrons flow from the anode to the cathode through the external circuit, creating an electrical current. This setup forms the basis for many practical applications, such as batteries.