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

• Molarity is # 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