Standard Reduction Potentials

Oct 13, 2025 by wbrum.org 127 views

Introduction

A galvanic cell, also known as a voltaic cell, is an electrochemical cell that generates an electric potential difference between two electrodes. It is a type of electrochemical cell that produces electricity through a spontaneous redox reaction. In this article, we will explore the concept of galvanic cells and determine the half-reactions for a galvanic cell with Zn and Mg electrodes.

What are Galvanic Cells?

A galvanic cell consists of two half-cells, each containing an electrode and an electrolyte. The electrodes are typically made of different materials, such as metals, and are immersed in an electrolyte solution. The electrolyte solution allows ions to move between the electrodes, facilitating the flow of electrons. The galvanic cell produces an electric potential difference between the two electrodes, which can be measured using a voltmeter.

Half-Reactions in Galvanic Cells

A half-reaction is a chemical reaction that occurs at one of the electrodes in a galvanic cell. There are two types of half-reactions: oxidation and reduction. Oxidation occurs at the anode, where electrons are released, while reduction occurs at the cathode, where electrons are gained.

Oxidation Half-Reaction

The oxidation half-reaction involves the loss of electrons from one of the electrodes. In the case of a galvanic cell with Zn and Mg electrodes, the oxidation half-reaction occurs at the Zn electrode. The reaction is as follows:

$ Zn(s) \rightarrow Zn^{2+}(aq) + 2e^{-} $

Reduction Half-Reaction

The reduction half-reaction involves the gain of electrons by one of the electrodes. In the case of a galvanic cell with Zn and Mg electrodes, the reduction half-reaction occurs at the Mg electrode. The reaction is as follows:

$ Mg^{2+}(aq) + 2e^{-} \rightarrow Mg(s) $

Determining the Correct Half-Reactions

To determine the correct half-reactions for a galvanic cell with Zn and Mg electrodes, we need to consider the standard reduction potentials of the two metals. The standard reduction potential is a measure of the tendency of a metal to lose or gain electrons. The metal with the more negative standard reduction potential will be the anode, while the metal with the more positive standard reduction potential will be the cathode.

Standard Reduction Potentials

The standard reduction potentials for Zn and Mg are as follows:

Zn: -0.76 V
Mg: -2.37 V

Determining the Anode and Cathode

Based on the standard reduction potentials, we can determine that the Mg electrode will be the anode, while the Zn electrode will be the cathode. The oxidation half-reaction will occur at the Mg electrode, while the reduction half-reaction will occur at the Zn electrode.

Correct Half-Reactions

The correct half-reactions for a galvanic cell with Zn and Mg electrodes are as follows:

Oxidation half-reaction: $ Mg(s) \rightarrow Mg^{2+}(aq) + 2e^{-} $
Reduction half-reaction: $ Zn^{2+}(aq) + 2e^{-} \rightarrow Zn(s) $

Conclusion

In conclusion, the half-reactions for a galvanic cell with Zn and Mg electrodes are $ Mg(s) \rightarrow Mg^{2+}(aq) + 2e^{-} $ and $ Zn^{2+}(aq) + 2e^{-} \rightarrow Zn(s) $. The Mg electrode is the anode, while the Zn electrode is the cathode. The oxidation half-reaction occurs at the Mg electrode, while the reduction half-reaction occurs at the Zn electrode.

References

Atkins, P. W., & De Paula, J. (2010). Physical chemistry. Oxford University Press.
Brown, T. E., & LeMay, H. E. (2014). Chemistry: The Central Science. Pearson Education.
Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2016). General chemistry: Principles and modern applications. Pearson Education.

Additional Resources

Khan Academy: Galvanic Cells
MIT OpenCourseWare: Electrochemistry
Chemistry LibreTexts: Galvanic Cells
Galvanic Cells: A Q&A Guide =============================

Introduction

In our previous article, we explored the concept of galvanic cells and determined the half-reactions for a galvanic cell with Zn and Mg electrodes. In this article, we will answer some frequently asked questions about galvanic cells.

Q: What is the purpose of a galvanic cell?

A: The purpose of a galvanic cell is to generate an electric potential difference between two electrodes. This potential difference can be used to power devices such as batteries, fuel cells, and electrochemical sensors.

Q: What are the two types of galvanic cells?

A: There are two types of galvanic cells: primary cells and secondary cells. Primary cells are non-rechargeable and can only be used once, while secondary cells are rechargeable and can be used multiple times.

Q: What is the difference between an anode and a cathode?

A: The anode is the electrode where oxidation occurs, while the cathode is the electrode where reduction occurs. In a galvanic cell, the anode is typically the electrode with the more negative standard reduction potential.

Q: What is the standard reduction potential?

A: The standard reduction potential is a measure of the tendency of a metal to lose or gain electrons. It is a value that is used to determine the potential difference between two electrodes in a galvanic cell.

Q: How do you determine the anode and cathode in a galvanic cell?

A: To determine the anode and cathode in a galvanic cell, you need to compare the standard reduction potentials of the two electrodes. The electrode with the more negative standard reduction potential will be the anode, while the electrode with the more positive standard reduction potential will be the cathode.

Q: What is the role of the electrolyte in a galvanic cell?

A: The electrolyte is a solution that allows ions to move between the electrodes in a galvanic cell. It facilitates the flow of electrons and helps to maintain the potential difference between the electrodes.

Q: Can you give an example of a galvanic cell?

A: Yes, a common example of a galvanic cell is a battery. A battery consists of two electrodes, a positive terminal and a negative terminal, separated by an electrolyte. When the battery is connected to a device, the electrons flow from the negative terminal to the positive terminal, generating an electric potential difference.

Q: What are some common applications of galvanic cells?

A: Galvanic cells have a wide range of applications, including:

Batteries: Galvanic cells are used to power devices such as flashlights, radios, and smartphones.
Fuel cells: Galvanic cells are used to generate electricity from chemical reactions.
Electrochemical sensors: Galvanic cells are used to detect and measure the concentration of ions in a solution.
Medical devices: Galvanic cells are used to power medical devices such as pacemakers and implantable cardioverter-defibrillators.

Q: What are some common challenges associated with galvanic cells?

A: Some common challenges associated with galvanic cells include:

Corrosion: Galvanic cells can be prone to corrosion, which can reduce their lifespan and performance.
Leaks: Galvanic cells can leak electrolyte, which can cause damage to the surrounding environment.
Safety: Galvanic cells can be hazardous if not handled properly, as they can cause electrical shock or fires.

Conclusion

In conclusion, galvanic cells are an important concept in chemistry and have a wide range of applications. By understanding the basics of galvanic cells, you can better appreciate the technology that powers many of the devices we use every day.

References

Atkins, P. W., & De Paula, J. (2010). Physical chemistry. Oxford University Press.
Brown, T. E., & LeMay, H. E. (2014). Chemistry: The Central Science. Pearson Education.
Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2016). General chemistry: Principles and modern applications. Pearson Education.

Additional Resources

Khan Academy: Galvanic Cells
MIT OpenCourseWare: Electrochemistry
Chemistry LibreTexts: Galvanic Cells