# Lecture 13: Introduction to Ideal (Gas) Mixtures | Summary and Q&A

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October 23, 2023
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MIT OpenCourseWare
Lecture 13: Introduction to Ideal (Gas) Mixtures

## TL;DR

Gas mixtures follow Dalton's law, where each component contributes a partial pressure in proportion to its mole fraction.

## Key Insights

• 🫢 Gas mixtures follow Dalton's law, where the partial pressure of each component is proportional to its mole fraction.
• 🫢 The change in Gibbs free energy determines whether a chemical reaction in a gas mixture is spontaneous.
• 🫢 Ideal gas mixtures do not interact, and each component behaves as if it undergoes an isothermal expansion.
• 🫢 Standard states for gases are defined as pure gases at the same temperature as the mixture but at one bar pressure.
• 👻 Balancing chemical reactions allows us to describe the change in moles as the reaction proceeds and simplifies calculations.

## Transcript

[SQUEAKING] [RUSTLING] [CLICKING] RAFAEL JARAMILLO: OK, so today we are starting a new topic. We're done with unary phase diagrams. We are going to start reacting gas systems. And it's useful, not just because it's useful and it's all right, but because it's an entree for solutions. So just a bit of topic here, we have start, and then we went to-- ... Read More

### Q: Why is it important to study gas mixtures in thermodynamics?

Gas mixtures are commonly encountered in various real-life applications, such as air composition and industrial processes. Understanding their behavior allows us to predict and control their properties.

### Q: What is the difference between components and elements in gas mixtures?

Components refer to the different gases present in the mixture, such as nitrogen or oxygen. Elements, on the other hand, are the individual chemical species that make up the components, like nitrogen atoms or oxygen molecules.

### Q: How is Dalton's law used to calculate partial pressures in gas mixtures?

Dalton's law states that the partial pressure of each component in a gas mixture is proportional to its mole fraction. By knowing the total pressure and mole fractions, we can calculate the partial pressures using the given formulas.

### Q: Can you explain the concept of chemical potential in gas mixtures?

Chemical potential refers to the potential of a component to undergo a chemical reaction. In gas mixtures, it can be calculated using Gibbs free energy and plays a crucial role in determining the direction and spontaneity of chemical reactions.

## Summary & Key Takeaways

• Gas mixtures involve multiple components in a homogeneous state, where each component contributes to the overall pressure in proportion to its mole fraction.

• Dalton's law states that the total pressure of a gas mixture is the sum of the individual partial pressures of each component.

• Chemical reactions in gas mixtures can change the components and/or phases involved, and the Gibbs free energy change determines whether the reaction is spontaneous or not.