Colligative Properties Chapter 13.6. Colligative Properties Collective-nature of Effect on 4...
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Transcript of Colligative Properties Chapter 13.6. Colligative Properties Collective-nature of Effect on 4...
![Page 1: Colligative Properties Chapter 13.6. Colligative Properties Collective-nature of Effect on 4 properties: 1) Vapor pressure lowering 2)Boiling point.](https://reader036.fdocuments.in/reader036/viewer/2022082410/5a4d1b7a7f8b9ab0599b8a9e/html5/thumbnails/1.jpg)
Colligative PropertiesChapter 13.6
![Page 2: Colligative Properties Chapter 13.6. Colligative Properties Collective-nature of Effect on 4 properties: 1) Vapor pressure lowering 2)Boiling point.](https://reader036.fdocuments.in/reader036/viewer/2022082410/5a4d1b7a7f8b9ab0599b8a9e/html5/thumbnails/2.jpg)
Colligative Properties• “Collective”-nature of• Effect on 4 properties: 1) Vapor pressure lowering2)Boiling point elevation3) Freezing point depression4) Osmotic pressure
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Electrolytes• Solutes dissolved in a solution can
separate into ions• These ions conduct electricity• Strong electrolytes (soluble • salts, strong acids and strong • bases) conduct current well • because they dissociate completely
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Raoult’s Law• Vapor pressure of the solvent over a solution
equals the mole fraction of solvent times the vapor pressure of the pure solvent; nonvolatile nonelectrolyte reduces vp.
• Psolvent = Xsolvent P°solvent
• Recognize that X is always <1 therefore, the new pressure is ALWAYS lower.
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Vapor Pressure Lowering• So when a solute is added to a solvent,
less solvent can escape and vapor pressure is lowered
• ΔP = X solute P°solvent
•
• Read Sample Problem 13.6; Put Follow-up Problem on Dry Erase boards
• http://www.kchemistry.com/AddedTopics_1.htm
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Boiling Point ElevationA solution boils at a higher temperature than the pure solventΔTb= boiling point elevation
ΔTb = Kb m
Kb = boiling pt elevation constant
m = solution molality
ΔTb= Tb(solution) - Tb(solvent)
![Page 7: Colligative Properties Chapter 13.6. Colligative Properties Collective-nature of Effect on 4 properties: 1) Vapor pressure lowering 2)Boiling point.](https://reader036.fdocuments.in/reader036/viewer/2022082410/5a4d1b7a7f8b9ab0599b8a9e/html5/thumbnails/7.jpg)
Boiling point Elevation
http://www.btinternet.com/~martin.chaplin/collig.html
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Freezing point depression
http://www.sparknotes.com/chemistry/solutions/colligative/section1.rhtml
![Page 9: Colligative Properties Chapter 13.6. Colligative Properties Collective-nature of Effect on 4 properties: 1) Vapor pressure lowering 2)Boiling point.](https://reader036.fdocuments.in/reader036/viewer/2022082410/5a4d1b7a7f8b9ab0599b8a9e/html5/thumbnails/9.jpg)
Freezing Point Depression• ΔTf = Kfm
• ΔTf = freezing point depression
• Kf = molal freezing point depression constant
• m = molal concentration of the solute
• ΔTf = Tf(solvent) – Tf(solution)
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Osmotic Pressure• Osmotic pressure is created when two solutions
are separated by a semipermeable membrane. The solvent can pass but not solute.
• Osmotic pressure: applied pressure required to prevent the net movement of water from solvent.
• II = nsoluteRT = MRT
• Vsoln
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Overarching Colligative Pts!
• Each property rests on the inability of solute particles to cross between two phases. The solute reduces the solution’s ability to change phase-freeze, boil, vaporize or move across a semipermeable membrane.
• Note: van’t Hoff factor
http://www.youtube.com/watch?v=a2qOZmuhDBI&feature=related
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Van’t Hoff factor• Strong electrolytes dissociate completely giving
2+ particles of solute per ionic compound. Example: MgCl2 dissolves into 3 particles unlike glucose.
• So: “i” = measured value for electrolyte solution»Expected value for nonelectrolyte»“i” = changes “m” on all colligative
properties
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Van’t Hoff Factor
http://www.kentchemistry.com/KentsDemos.htm
http://www.youtube.com/watch?v=SX5V7kzmGeU