0314 enthalpy change associated with dispersal of

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03:14 enthalpy change associated with dispersal of gaseous solute in water Gdelta=Hdelta-T*Sdelta for free energy Sdelta provides the principle driving force for the behavior summarized by like dissolves  like Spontaneity (neg Gdelta) When nonppolar substance is introduced to water, the water molecules break up to form  a highly ordered cage around the nonpolar substance, which makes a negative  contribution to the entropy of solution and in certain cases leads to negative Sdelta(soln)  value Unfavorable entropy contribution is why nonpolar substances are insoluble in water 17.3 factors affecting solubility pressure increases the solubility of a gas Henry’s Law P=KhX P=parital pressure of gaseous solute above the solution X=mole fraction of dissolved gas Kh=constant Amount of gas dissolved in a solution is directly proportionate the pressure of the gas  above the solution Dissolving occurs more rapidly at higher temp but amount of solid that can be dissolved  may increase or decrease with increasing temp Gases become more soluble in most nonaqueous solvents as temp increases 17.4 vapor pressures of solution add antifreeze to the water in a cars cooling system to prevent freezing in winter and  boiling in summer nonvolatile solute as no tendency to escape from solution into the vapor phase Raoult’s Law Psoln=Xsolv*P(not)solv
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03:14 Xsolv = mole fraction of solvent Ideal solution- any solution that obeys Raoult’s law If observed vapor pressure is lower than predicted by R’s law then there is a egative  deviation Ptotal=Pa+Pb=XaPa+XbPb 17.5 boiling-point elevation and freezing-point depression colligative properties BP elevation Nonvolatile solute elevates the boiling point of solvent Tdelta=Kb*m(solute) FB depression Water in the solution has a lower vapor pressure than that of pure ice Antifreeze Tdelta=Kf*m(solute) 17.6 Osmotic pressure semipermiable membrane-allows solvent but not solute molecules osmosis- flow of solvent into the solution through the semipermiable membrane the pressure that just stops the osmosis is equal to the osmotic pressure of the solution pi=MRT dialysis-semipermiable membrane allows transfer of both solvent molecules and small  solute molecules and ions isotonic solutions- solutions that have identical osmotic pressures reverse osmosis-
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03:14 if a solution in contact with pure solvent across a semipermeable membrane is  subjected to an external pressure larger than its osmotic pressure desalination- removal of dissolved salts  17.7 colligative properties of electrolyte solution van’t Hoff factor i= moles of particles in solution/moles of solute dissolved count of ions present
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