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Solutions. Solution – homogenous mixture so evenly mixed that individual particles can not be seen Solution – made of solute and solvent Solvent – dissolves a substance Solute – substance that is dissolved. Solutions – how they form. solution formed when solvent dissolves solute
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Solutions • Solution – homogenous mixture so evenly mixed that individual particles can not be seen • Solution – made of solute and solvent • Solvent – dissolves a substance • Solute – substance that is dissolved
Solutions – how they form • solution formed when solvent dissolves solute • rate of dissolving affected by surface area of solute, temp. of solvent, stirring (agitation) of solution • agitation will only affect rate of dissolving, not overall amount of solute dissolved
Solubility • based on KTOM(idea that all matter is moving) • dissolving is constantly occurring & reversing simultaneously • when this point is reached, have saturated solution • holds all solute it can at that temp.
Solubility continued • solubility is amt. of solute dissolving in a given amt of solvent at certain temp. to create sat. solution • unsaturated solution holds less solute than CAN at that temp.
Factors affecting Solubility • solubility of solid usually rises as temp. of solvent rises • gases dissolve better in cold liquids, why? (hint: KTOM) • gas solubility increases as the partial pressure of gas above liquid solvent increases (think COKE!)
Factors affecting solubility - 2 • miscible – applies to liquids, will dissolve in each other • Henry's Law (for given temp.) __S1__ = __S2__ P1 P2
Concentrations • measure of amt of solute/given amt of solvent • dilute (low conc. of solute) and concentrated (high conc. of solute) are qualitative descriptions • Molarityis # of moles solute /Liter sol'n (also known as molar concentration) • Dilution reduces moles solute/unit volume but total moles of solute in sol'n doesn't change, so M1V1 = M2V2
Colligative properties vapor-pressure lowering • VP is Pressure exerted by vapor above a liquid • the decrease in VP is proportional to the number of particles in the solution • EX: (NaCl makes many particles, lowers VP more than glucose, which makes less)
Colligative properties • boiling point elevation • BP is temp where Vapor Pressure of liquid = atmospheric Pressure • When the VP decrease, Boiling Point increases • need more KE to raise VP to atmospheric Pressure due to greater attraction btw particles • BP of solution > BP of pure solvent (so salt doesn’t make water boil faster!)
Colligative properties • freezing point depression • FP lowered due to formation of "shells of solvation", groupings of particles that are attracted to one another • freezing these "shells" requires removal of more KE than freezing pure solvent, lowering FP • size of depression is proportional to # of solute particles dissolved in solvent