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# MIT 5.60 Thermodynamics & Kinetics Spring 2008 Lecture #22 Quiz

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@OverjoyedDogwood

### Explain the difference between ideal and non-ideal solutions in terms of molecular interactions.

Ideal solutions have no interactions between molecules, while non-ideal solutions involve interactions between molecules.

### What is the significance of ∆u in determining the behavior of solutions?

∆u determines how solutions depart from ideality.

### How does ∆H differ in ideal and non-ideal solutions?

In non-ideal solutions, ∆H is approximately equal to ∆U, while in ideal solutions, there is no enthalpy change.

### Describe positive deviations in solutions and their effect on mixing.

<p>Positive deviations indicate that mixing is energetically not favorable, leading to non-ideal behavior.</p> Signup and view all the answers

### What determines how solutions depart from ideality?

<p>The difference in molecular interactions, specifically ∆u, determines how solutions depart from ideality.</p> Signup and view all the answers

### Explain the formula for ∆Gmix in non-ideal solutions.

<p>∆Gmix = n ∆u + nRT ( xA ln xA + xB ln xB )</p> Signup and view all the answers

### What is the condition for a positive deviation from Raoult's Law?

<p>pCS = pB*</p> Signup and view all the answers

### Explain why mixing acetone and chloroform results in a negative deviation from Raoult's Law.

<p>H-bonding attraction</p> Signup and view all the answers

### What is the condition for an ideal dilute solution according to the text?

<p>xCS2 = xB → 1</p> Signup and view all the answers

### When does Henry's Law apply in the context of ideal dilute solutions?

<p>xB → 0 (B is the 'solute')</p> Signup and view all the answers

### What does the Henry's Law constant, KB, depend on?

<p>Solvent/solute mixture and temperature</p> Signup and view all the answers

### What is the consequence of a positive deviation in Henry's Law?

<p>KB &gt; pB*</p> Signup and view all the answers

## Study Notes

### Two-Component Phase Equilibria III

#### Ideal Solutions

• Free energy change in ideal solutions: ∆Gmix = nRT ( xA ln xA + xB ln xB )
• ∆Gmix is purely entropic, similar to gas mixtures
• No enthalpy change (∆Hmix = 0) and no volume change (∆Vmix = 0)

#### Non-Ideal Solutions

• Molecular interactions: uAA, uBB, and uAB determine the deviation from ideality
• ∆u = 2uAB - (uAA + uBB) determines how solutions depart from ideality
• Positive deviations: ∆u > 0, mixing is energetically not favorable
• Negative deviations: ∆u < 0, mixing is energetically favorable

### Deviations from Raoult's Law

#### Positive Deviations

• Example: acetone and carbon disulphide
• ∆Gmix > ∆Gmix (ideal)
• Vapor pressure is higher than expected by Raoult's Law

#### Negative Deviations

• Example: acetone and chloroform
• ∆Gmix < ∆Gmix (ideal)
• Vapor pressure is lower than expected by Raoult's Law

### Ideal Dilute Solutions and Henry's Law

#### Ideal Dilute Solution

• Defined by limits xB → 1 and xB → 0
• Raoult's Law applies for the solvent (xB → 1)
• Henry's Law applies for the solute (xB → 0)

#### Henry's Law

• pCS = xCS KCS
• KB is the Henry's Law constant, dependent on the solvent/solute mixture and temperature
• Positive deviation: KB > pB*
• Negative deviation: KB < pB*

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## Description

Test your knowledge on Two-Component Phase Equilibria III, Ideal and Non-Ideal Solutions, and Free energy change in ideal solutions. Explore concepts related to ∆Gmix and its calculation in different liquid solutions.

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