SolutionsSolutions

Chm 3.2Chm 3.2

SolutionsSolutions

Solute – substance dissolvingSolute – substance dissolving

Solvent – substance solute is Solvent – substance solute is dissolved indissolved in– (substance you have in greatest (substance you have in greatest

amount)amount)

Solution – solvent + soluteSolution – solvent + solute

Types of SolutionsTypes of Solutions

Solids – alloys (metal mixtures)Solids – alloys (metal mixtures) Liquids – sugar or salt in waterLiquids – sugar or salt in water Gases – airGases – air Suspensions – solute particles so large Suspensions – solute particles so large

they settle out (muddy water)they settle out (muddy water) Colloids – solute particles are sized in-Colloids – solute particles are sized in-

between solution and suspensionbetween solution and suspension Homogeneous - solutionsHomogeneous - solutions Heterogeneous – colloids, suspensionsHeterogeneous – colloids, suspensions

Electrolyte vs Non-Electrolyte vs Non-electrolyteelectrolyte

Electrolyte – substance that dissolves Electrolyte – substance that dissolves to form a solution that conducts to form a solution that conducts electricityelectricity

Non-electrolyte – substance that Non-electrolyte – substance that dissolves to form a solution that dissolves to form a solution that DOES NOT conduct electricityDOES NOT conduct electricity

Factors affecting Rate of Factors affecting Rate of DissociationDissociation

Rate depends on Solute/Solvent Rate depends on Solute/Solvent Interactions or AttractionInteractions or Attraction

– Increasing Surface AreaIncreasing Surface Area

– Agitating a SolutionAgitating a Solution

– Heating (more KE = more collisions)Heating (more KE = more collisions)

SolubilitySolubility Solubility has a limitSolubility has a limit Solution equilibrium – opposing processes Solution equilibrium – opposing processes

of dissolution and crystallization occuring of dissolution and crystallization occuring at equal ratesat equal rates

Saturated Solution – contains the max Saturated Solution – contains the max amount of solute amount of solute

Unsaturated Solution – contains less solute Unsaturated Solution – contains less solute than a saturated solutionthan a saturated solution

Supersaturated Solution – more dissolved Supersaturated Solution – more dissolved solute than a saturated solution under the solute than a saturated solution under the same conditionssame conditions

Measuring SolubilityMeasuring Solubility

The amount of substance required to The amount of substance required to form a saturated solution with a form a saturated solution with a specific amount of solvent at a specific amount of solvent at a specific temperaturespecific temperature

Solubility varies with temperatureSolubility varies with temperature Rate of a solid dissolving is not Rate of a solid dissolving is not

related to solubilityrelated to solubility

Dissolving Ionic Compounds in Dissolving Ionic Compounds in Water (Hydration)Water (Hydration)

Polar water attracts + and – ionsPolar water attracts + and – ions Water molecules surround ionsWater molecules surround ions Ions are drawn away from surface of Ions are drawn away from surface of

the crystalthe crystal HydratesHydrates

– Some ionic compounds will re-crystallize Some ionic compounds will re-crystallize with water molecules attachedwith water molecules attached

CuSOCuSO44 · 5H· 5H22OO

Like Dissolves LikeLike Dissolves Like

Polar dissolves in polarPolar dissolves in polar Non-polar DOES NOT dissolve in polarNon-polar DOES NOT dissolve in polar

Immiscible – Immiscible – – Liquid solvents and solute that are not Liquid solvents and solute that are not

solublesoluble Miscible – Miscible –

– Liquids that dissolve freely in eachotherLiquids that dissolve freely in eachother

Gas SolubilityGas Solubility

PressurePressure– Increasing pressure = stress on EQIncreasing pressure = stress on EQ– More molecules collide with surface of More molecules collide with surface of

liquidliquid– EQ shifts so fewer molecules are in gas EQ shifts so fewer molecules are in gas

phasephase– Increases solubilityIncreases solubility– Henry’s LawHenry’s Law – – solubility of gas is directly solubility of gas is directly

proportional to pressure of the gas on proportional to pressure of the gas on surface of liquidsurface of liquid

Temperature and SolubilityTemperature and Solubility

Gas Solubility in LiquidsGas Solubility in Liquids– Increase temperature = less gas Increase temperature = less gas

dissolveddissolved

Solid Solubility in LiquidsSolid Solubility in Liquids– Increasing temperature increases Increasing temperature increases

solubility in SOME casessolubility in SOME cases

Concentration of SolutionsConcentration of Solutions

MolarityMolarity

moles of solute per liter of solutionmoles of solute per liter of solution

n

LM =

Molarity ExamplesMolarity Examples

1.1. You have 3.50L of solution that contains You have 3.50L of solution that contains 90.0g of sodium chloride. What is the 90.0g of sodium chloride. What is the molarity of the solution?molarity of the solution?

2. You have 0.8 L of a 0.5 M HCl solution. How 2. You have 0.8 L of a 0.5 M HCl solution. How many moles of HCl does this solution many moles of HCl does this solution contain?contain?

3. What volume of a 6.0M potassium chromate 3. What volume of a 6.0M potassium chromate solution is needed to ensure that 23.4g of solution is needed to ensure that 23.4g of potassium chromate are in the solution?potassium chromate are in the solution?

DilutionDilution

DilutingDiluting– Taking a solution of one concentration and Taking a solution of one concentration and

adding solvent to lower the concentrationadding solvent to lower the concentration

MM11VV11 = M = M22VV22

The concentration x volume of initial The concentration x volume of initial solution is equal to the concentration x solution is equal to the concentration x volume of the final solution. volume of the final solution.

Dilution

water (solvent) solute

concentrated, Minitial

diluted, Mfinal

adding water lowers the solute concentration

moles of solute remain constant

Vinitial

Vfinal

molesinitial = molesfinal

Mfinal x Vfinal = Minitial x Vinitial

Dilution ExamplesDilution Examples

1.1. What volume of a 5.0 M stock HCl What volume of a 5.0 M stock HCl solution is needed to produce 1.5L solution is needed to produce 1.5L of a 2.5M HCl solution?of a 2.5M HCl solution?

2.2. What will the new concentration be What will the new concentration be when a 0.3 M solution of NaOH is when a 0.3 M solution of NaOH is diluted from 1.0 L to 2.5 L?diluted from 1.0 L to 2.5 L?

Colligative PropertiesColligative Properties

Properties of solutions that depend Properties of solutions that depend on the concentration of solute on the concentration of solute particles dissolvedparticles dissolved

1.1. Vapor Pressure LoweringVapor Pressure Lowering

2.2. Freezing Point DepressionFreezing Point Depression

3.3. Boiling Point ElevationBoiling Point Elevation

4.4. Osmotic PressureOsmotic Pressure