Dilute vs. Concentrated Concentrated solutions Concentrated solutions contain a high amount of solute. Diluted solutions Diluted solutions contain a low amount of solute. ~ ‘strong’ ~ ‘weak’ These terms are not very helpful when describing solution concentration b/c they are completely relative. 1 gram of solute compared to 10 grams = 1 gram of solute compared to 0.1 grams = dilute concentrated

Types of Solutions Unsaturated solutions Unsaturated solutions contain a less solute than they are capable of dissolving at a given T and P. ~ can hold more…not full yet! Saturated solutions Saturated solutions contain the max. amount of solute that they are capable of dissolving at a given T and P. ~ equilibrium exists b/n dissolved and undissolved solute. ~ completely full, can’t hold any more! Supersaturated solutions Supersaturated solutions contain more solute (dissolved) than it is supposed to hold at a given T and P. ~ must heat solution up to allow more solute to dissolve ~ then let it cool down very slowly, undisturbed.

Solution Calculations we said that ‘dilute’ and ‘concentrated’ are very general terms for solution concentration. Molarity Molarity indicates how many moles of solute are dissolved in one liter of solution. moles Liters ~ units = M Ex… What is the molarity of a salt water solution containing 9.0 moles of salt dissolved in 3.0 liters of solution? 9.0 moles 3.0 liters = 3.0 M 3.0 M ~ molarity =

What is the molarity of 174 grams of NaCl dissolved in mL of solution? Ex… ~ molarity = moles Liters grams mL 58 grams NaCl 1 mole 1000 mL 1 liter = 6.00 M 6.00 M

Other types of solution concentration include… % mass ~ % mass = part whole = mass of solute or solvent mass of solution 100 x Ex… What is the % by mass of 62.0 grams of KCl dissolved in 475 grams of water ? solvent part (solute) % mass = part whole % mass = = 11.5% 11.5% ** whole = solution… solute + solvent! = 537 grams of solution 100 x

Ex… How many grams of KOH are required to prepare grams of a 30.0% solution? whole (solution) % part (solute) % mass = part whole x x part = % x whole KOH = x = 135 g 135 g

Dilution calculations… ~ a dilution = a solution is made less concentrated (weaker) by adding more solvent. M 1 V 1 = M 2 V 2 M 1 V 1 = M 2 V 2  changes concentration (molarity).  changes volume of solution. initial molarity initial volume final molarity final volume

Ex… How many liters of a 12M solution are needed to create 2.0 liters of a 4.0M solution? M 1 V 1 = M 2 V 2 M 1 V 1 = M 2 V 2 M 1 V 1 V 2 M 2 12 X 2.0 (4.0) = 0.67 liters 0.67 liters 12 X = X= Ex… What is the molarity of 1.5 liters of solution made from mL of 10.0M NaOH? V 1 M 1 V 2 M X (10.0) = 1.5 X = M 4.0M X=

Precipitates Precipitate : Precipitate : insoluble an insoluble solid that will separate from a solution during a reaction (double displacement). ~ using solubility rules, we can predict precipitates. CompoundSolubilityExceptions Salts of group 1A and ammonia (NH 3 ) Soluble (aq)Some lithium compounds Ethanoates, nitrates, chlorates, and perchlorates Soluble (aq)Few Exceptions Sulfates (SO 4 )Soluble (aq) Compounds of Pb, Ag, Hg, Ba, Sr, and Ca Chlorides, Bromides, and Iodides Soluble (aq) Compounds of Ag and some of Hg and Pb Sulfides and HydroxidesInsoluble (s) Group 1A compounds. Compounds of Ba, Sr, and Ca (slightly) Carbonates, Phosphates, and Sulfites Insoluble (s) Group 1A and ammonia (NH 3 ) compounds

Predict the precipitate… CompoundSolubilityExceptions Salts of group 1A and ammonia (NH 3 )Soluble (aq)Some lithium compounds Ethanoates, nitrates, chlorates, and perchlorates Soluble (aq)Few Exceptions Sulfates (SO 4 )Soluble (aq) Compounds of Pb, Ag, Hg, Ba, Sr, and Ca Chlorides, Bromides, and IodidesSoluble (aq) Compounds of Ag and some of Hg and Pb Sulfides and HydroxidesInsoluble (s) Group 1A compounds. Compounds of Ba, Sr, and Ca (slightly) Carbonates, Phosphates, and SulfitesInsoluble (s) Group 1A and ammonia (NH 3 ) compounds LiI (aq) + AgNO 3 (aq) LiNO 3 LiNO 3 + AgI AgI (aq) (s) *precipitate* NaOH (aq) + Cr 2 (SO 4 ) 3 (aq) Na 2 SO 4 Na 2 SO 4 + Cr(OH) 3 Cr(OH) 3 (aq)(s) *precipitate*

Electrolytes vs. Non-Electrolytes Electrolytes : dissociate in water readily and conduct an electric current.  Any ionic compounds, some covalent compounds Non-electrolytes : dissolve in water, but don’t dissociate or conduct an electric current.  All sugars and other covalent compounds

Colligative Properties Colligative properties Colligative properties are properties of solutions that are affected only by the # of particles in the solution. NOT affected by the type of particle!!! Ex… ~ vapor pressure (VP) ~ freezing point (FP) ~ boiling point (BP)

Effect of Solutes on Vapor Pressure Vapor pressure (VP) Vapor pressure (VP) is the P exerted at the surface of a liquid by particles trying to escape the liquid.

adding a nonvolatile solute to a solvent will cause the VP of the solvent to decrease. ~ solute particles replace some solvent particles at the surface of the solution ~ less solvent particles on surface = less evaporation = lower VP!

How Solutes Affect BP and FP Boiling Point (BP) is temp. at which the VP of the liquid = atmospheric pressure. ~ adding solute lowers VP of solvent ~ must add more KE (heat) to equalize the pressures ** solutes RAISE the BP of solutions! (i.e. we add salt before we boil water) pure watersalt water

Freezing Point (FP) is temp. at which liquid turns into a solid. ~ enough KE is lost (removal of heat) that molecules stop moving around and lock into place. ~ adding solute lowers VP of solvent ~ even more KE (heat) must be lost to lock molecules into place. ** solutes LOWER the FP of solutions! (i.e. we add salt to icy roads…salt is used in making ice cream )

Ionic solutes lower the VP of solvents more than molecular solutes! ~ ionic solutes dissociate (break up into ions) in solvents. AlCl 3 dissociates into 4 separate ions (1 Al +3 and 3 Cl -1 ) ~ molecular solutes stay intact in solvents. glucose (C 6 H 12 O 6 ) breaks into separate units of C 6 H 12 O 6 … NOT C’s, H’s and O’s! glucose = Al +3 = Cl -1