Overall more energy is released in step 3 than the

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Overall, more energy is released in step 3 than the energy required in steps 1 and 2 o Its energetically favorable (delta H<0) for KCL to dissolve in water o KCL dissolving in water is both energetically and entropically favorable o If Delta H <0: Solubility is energetically favored Spontaneous process tend to be exothermic Not all processes are exothermic Entropy: o Thermodynamic measure of disorder/randomness 2 nd law of thermodynamics: o In order of anything to happen spontaneously, overall entropy must increase Driving forces for solubility: o Overall decrease in energy (delta H < 0) o Overall increase in entropy (delta S < 0) o “like dissolve like” Ionic and polar compounds are more soluble in polar solvents Nonpolar compounds are more soluble in nonpolar solvents Solubility: o Maximum amount of solute that can be dissolved in a particular amount of solvent Temperature and Pressure Effects: o Increase in temperature : Increases the solubility of most solids in liquid solvents Higher temperature means increased motion o Helps overcome attractive forces in a sold Decreases the solubility of a gas in a liquid solvent Higher temperatures allow gas particles to move fast enough to escape the liquid o Increase in pressure: Increases solubility of a gas in that solution Higher pressure forces gas particles to contact liquid surfaces more often Colligate Properties: o Physical property of a solution that depends on the total number of solute particles present, but not their identity o Types: Vapor Pressure (VP) Lowering:
CHEM 113 EXAM 4 Adding a nonvolatile solute to a solvent lowers the VP according to Raoult’s Law Pa = Xa * Poa Pa= new VP Xa = mole fraction Poa= VP of pure solvent Boiling Point (BP) Elevation: The boiling point of a solution is higher than that of a pure liquid according to: Change in Tb = Kb *m Change in Tb = BP elevation Kb = molar BP elevation constant M = molality of solution = moles of solute / kg of solvent EXAMPLES: o Car radiator coolant o Adding salt to boil water for cooking pasta Freezing/melting point depression: Freezing/melting point of a solution is lower than that of a pure liquid according to: Change in Tf = Kf* m Change in Tf = freezing point depression Kf = constant M = molality of solution EXAMPLES: o Car radiator antifreeze Osmosis: The net movement of solvent through semi permeable membrane toward the solution with the greater solute concentration Pi = (n/V) *R*T = MRT Pi = osmotic pressure (pressure when net movement stops

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