Lec 23 | MIT 5.112 Principles of Chemical Science, Fall 2005

TL;DR

Electrolysis is a process that uses an external voltage to force a non-spontaneous reaction to occur, such as the reduction of magnesium ions to magnesium metal. The Nernst equation is used to calculate the potential of a cell based on the concentrations of the reactants.

Transcript

The following content is provided by MIT OpenCourseWare under a Creative Commons license. Additional information about our license and MIT OpenCourseWare in general is available at ocw.mit.edu. Today I will begin by talking about a subject that we were just getting to at the end of class last time, and that will be electrolysis. And this is an inte... Read More

Key Insights

• 👻 Electrolysis allows for the non-spontaneous reactions to occur by applying an external voltage.
• ❓ The Nernst equation relates the potential of a cell to the concentrations of the reactants.
• 😑 Concentration cells can generate a potential difference by having different concentrations of ions on either side.

Questions & Answers

Q: What is electrolysis and how does it work?

Electrolysis is a process that uses an external voltage to force a non-spontaneous reaction to occur. By applying a potential difference between positive and negative electrodes immersed in a molten salt, the reaction can be driven in the desired direction.

Q: How does the Nernst equation calculate the potential of a cell?

The Nernst equation is E = E0 - (RT/nF) * ln(Q), where E is the potential of the cell, E0 is the standard cell potential, R is the gas constant, T is the temperature, n is the number of electrons transferred in the reaction, F is Faraday's constant, and Q is the reaction quotient.

Q: How can concentration cells be used to generate a potential difference?

Concentration cells can be set up by having different concentrations of ions on either side of the cell. This concentration difference results in a potential difference, with ions moving from the higher concentration side to the lower concentration side.

Q: What is the purpose of the Nernst equation in electrolysis?

The Nernst equation allows for the calculation of the potential of a cell at non-standard conditions, such as different reactant concentrations. This is useful in electrolysis, as it helps predict the potential required to drive the desired reaction.

Summary & Key Takeaways

• Electrolysis can be used to carry out non-spontaneous reactions by applying an external voltage.

• The Nernst equation relates the potential of a cell to the concentrations of the reactants.

• Concentration cells can be set up by having different concentrations of ions on either side of the cell to create a potential difference.