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lecture 8

lecture 8 - Effect of Temperature on Solubility of a Gas...

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Unformatted text preview: Effect of Temperature on Solubility of a Gas: For all gases solubility with temperature This is due to Le Chatlier's Principle 1 ... Today's take home messages! Vapor Pressure Lowering Boiling Point Elevation Freezing Point Depression ... 2 Understanding Colligative Properties VP of H2O over a solution depends on the number of H2O molecules per solute molecule. Psolvent proportional to Xsolvent ... 3 Vapor Pressure Lowering ... Figure 14.14 4 Raoult's Law With 2-components where A is the solvent and B 2is the solute VP lowering is proportional to mol frac solute! solute! For very dilute solutions, where K is a proportionality constant. constant. This helps explain changes in melting and boiling points. ... 5 Changes in Freezing and Boiling Points of Solvent VP Pure solvent 1 atm P VP solvent after adding solute BP solution T ... 6 BP pure solvent Boiling Point Changes The boiling point of a solution is higher than that of the pure solvent. ... 7 Boiling Point Elevation VP Pure solvent 1 atm P VP solvent after adding solute BP solution T ... 8 BP pure solvent Change in Boiling Point If we dissolve 62.1 g of glycol (1.00 mol) in 250. g of water. What is the BP of the solution? KBP = +0.512 oC/molal for water ... 9 Change in Freezing Point Pure water Ethylene glycol/water solution The freezing point of a solution is LOWER than that of the pure solvent. solvent. ... 10 Lowering the Freezing Point Water with and without antifreeze When a solution freezes, the solid phase is pure water. The solution becomes more concentrated. ... 11 Freezing Point Depression Calculate the freezing point of a 4.00 molal glycol/water solution. Kfp = -1.86 oC/molal p ... 12 Boiling Point Elevations and Freezing Point Depressions with ions i = van't Hoff factor = number of particles produced per formula unit. Compound Ethylene glycol NaCl CaCl2 Theoretical Value of i 1 2 3 ... 13 Freezing Point Depression Q: How much NaCl must be dissolved in 4.00 kg of water to lower the freezing point to -10.00 oC? (Kfp = -1.86 oC/molal) ... 14 Freezing Point Depression Q: How much NaCl must be dissolved in 4.00 kg of water to lower the freezing point to -10.00 oC? (Kfp = -1.86 oC/molal) ... 15 Boiling & freezing point constants ... UMass Amherst Biochemistry Teaching Initiative ...
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