Chapter 12-13:Chapter 12-13:MixturesMixtures and and Aqueous Aqueous

SolutionsSolutions

What are they?What are they?

Where do we find them?Where do we find them?

How do we describe them?How do we describe them?

We use solutions all the time

Soluble versus insolubleSoluble versus insoluble• Some solids are soluble in water, ie: table Some solids are soluble in water, ie: table

salt, NaCl. salt, NaCl. Soluble Soluble means: means: able to be able to be dissolveddissolved..

• Soluble Soluble ionic solidsionic solids (made of cation and (made of cation and anion) anion) dissociate into their ionsdissociate into their ions in water. in water.

• Soluble Soluble covalent solidscovalent solids (like sugar) (like sugar) dissolve because they are dissolve because they are relatively relatively polarpolar..

BackBack

Bires, 2005 Slide 3

• In a solution, the dissolved particles In a solution, the dissolved particles cannot be easily seen or separated from cannot be easily seen or separated from the solution.the solution.

• Alloys are solutions of metals!Alloys are solutions of metals!

Parts of a Parts of a solutionsolution• The The dissolving mediumdissolving medium is the is the solventsolvent

(what does the dissolving)(what does the dissolving)

• The The dissolved substancedissolved substance is the is the solutesolute (what gets dissolved)(what gets dissolved)

• The The solute solute andand solventsolvent togethertogether form form the the solutionsolution..

• Solvents and solutes can be any Solvents and solutes can be any phasephase..

solution

Special types of mixtures - Special types of mixtures - SuspensionsSuspensions

• SuspensionsSuspensions– mixtures where the solutes mixtures where the solutes

particles are particles are very largevery large, so they , so they don’tdon’t completely completely dissolvedissolve into into their solvent.their solvent.

• Solute particles will settle out Solute particles will settle out of the solution if left of the solution if left undisturbed. – this creates two undisturbed. – this creates two phasesphases..

• Muddy water and Italian salad Muddy water and Italian salad dressing are good examples of dressing are good examples of suspensions.suspensions.

Special types of mixtures - Special types of mixtures - ColloidsColloids

• ColloidsColloids– mixtures where the solute particle is mixtures where the solute particle is smaller smaller

than particles in a suspensionthan particles in a suspension, but , but not small not small enough to dissolveenough to dissolve..

• Colloids have two Colloids have two phasesphases::Dispersed phaseDispersed phase – the – the solutesoluteDispersing mediumDispersing medium – the – the solventsolvent..

BackBack

Bires, 2005 Slide 7

ColloidsColloids• Mayonnaise and hair gel are good Mayonnaise and hair gel are good

examples of colloids.examples of colloids.

• There are 7 types of colloids, found on There are 7 types of colloids, found on page 404…page 404…

7 Types of Colloids7 Types of ColloidsPage 404

Two groups of colloids:

Heterogeneous colloids – two phases are clearly seen

Homogeneous colloids – appears to be one phase

Colloid TypeColloid Type PhasesPhases ExampleExample

SolSol solid in liquid, liquid substancesolid in liquid, liquid substance PaintPaint

GelGel solid in liquid, solid substancesolid in liquid, solid substance GelatinGelatin

FoamFoam gas in liquidgas in liquid Whipped creamWhipped cream

Liquid Liquid EmulsionEmulsion

liquid in liquidliquid in liquid Milk, mayonnaiseMilk, mayonnaise

Solid Solid EmulsionEmulsion

liquid in solidliquid in solid Cheese, butterCheese, butter

Solid AerosolSolid Aerosol solid in gassolid in gas SmokeSmoke

Liquid Liquid AerosolAerosol

liquid in gasliquid in gas Clouds, fogClouds, fog

The Tyndall EffectThe Tyndall Effect

The Tyndall effect allows us to distinguish between solutions, colloids, and suspensions.

It works by shining a beam of light into the mixture. If…

John Tyndall, Brittish, c1860

BackBack

Bires, 2005 Slide 10

Results of Tyndall EffectResults of Tyndall Effect• Light doesn’t pass through

– the mixture is a suspension or a heterogeneous colloid.

• Light passes through unobstructed– the mixture is a solution.

• Light passes, but the beam can be seen in the mixture– the mixture is a homogeneous colloid

BackBack

Bires, 2005 Slide 11

The Tyndall EffectThe Tyndall Effect

ElectrolytesElectrolytes• ElectrolytesElectrolytes

– Solutions that Solutions that conduct electricityconduct electricity..

• Ionic solutionsIonic solutions are are electrolyteselectrolytes..

• Covalent solutionsCovalent solutions are are nonelectrolytesnonelectrolytes..

BackBack

Bires, 2005 Slide 13

What do you think?What do you think?

Is saltwater (NaCl in water) an electrolyte?Is saltwater (NaCl in water) an electrolyte?

Is sugar water (CIs sugar water (C66HH1212OO66 in water) an in water) an electrolyte?electrolyte?

Conductivity tester (meter)Conductivity tester (meter)– can tell us if a solution is an electrolyte, and can tell us if a solution is an electrolyte, and

sometimes, how sometimes, how strongstrong an electrolyte is. an electrolyte is.

BackBack

Bires, 2005 Slide 14

Warm Up- Would the following solutes be Warm Up- Would the following solutes be electrolytes or nonelectrolyteselectrolytes or nonelectrolytes

CaClCaCl22

CClCCl44

SrBrSrBr22

How do you know??How do you know??

BackBack

Bires, 2005 Slide 15

Warm UpWarm Up

Be sure you hand in any HW that you may Be sure you hand in any HW that you may not have had on test day…not have had on test day…

Article AnalysisArticle Analysis

ReviewReview

12.2 Enthalpy WS12.2 Enthalpy WS

10.4 and 16.1 Notes10.4 and 16.1 Notes

SolubilitySolubility• SolubilitySolubility

– The extent to which a solute will dissolve in a The extent to which a solute will dissolve in a solvent. solvent. (how (how muchmuch solute will dissolve) solute will dissolve)

• High solubilityHigh solubility– large amounts of solute will dissolve in a large amounts of solute will dissolve in a

solventsolvent

• Low solubilityLow solubility– only small amounts of solute will dissolveonly small amounts of solute will dissolve

BackBack

Bires, 2005 Slide 17

SolubilitySolubility• Increasing temperature Increasing temperature increasesincreases the the

solubility of solubility of solidssolids in liquids. in liquids.

• Increasing temperature Increasing temperature decreasesdecreases the the solubility of solubility of gasesgases in liquids! … in liquids! …

BackBack

Bires, 2005 Slide 18

Reading Solubility CurvesReading Solubility Curves

Solid-LiquidSolid-Liquid solubility with solubility with temperaturetemperature

BackBack

Bires, 2005 Slide 20

Gas-LiquidGas-Liquid solubility with solubility with temperaturetemperature

Gases in liquidsGases in liquids• In addition to cold In addition to cold

temperatures, temperatures, high high pressures increase pressures increase solubilitysolubility of gases of gases in liquids.in liquids.

• Henry’s LawHenry’s Law::– solubility of a gas in solubility of a gas in

a liquid increases a liquid increases with increasing with increasing pressure of that gas pressure of that gas above the liquid.above the liquid.

Like Dissolves Like!Like Dissolves Like!• Some solvents are Some solvents are polarpolar, having , having partialpartial negative negative

and partial positive endsand partial positive ends. (. (HH22OO))

• Other solvents are Other solvents are nonpolarnonpolar, having no “+” “-” , having no “+” “-” polespoles

• Polar solutes tend to dissolve well in polar Polar solutes tend to dissolve well in polar solventssolvents……

• Nonpolar solutes tend to dissolve well into Nonpolar solutes tend to dissolve well into nonpolar solventsnonpolar solvents..

BackBack

Bires, 2005 Slide 23

Like Dissolves LikeLike Dissolves Like

Water is very polar. Does it dissolve polar Water is very polar. Does it dissolve polar substances or non polar substance?substances or non polar substance?

SaturationSaturation• Saturated SolutionSaturated Solution

– solution has as much solute in it as it will solution has as much solute in it as it will allow (equal to solubility)allow (equal to solubility)

• Unsaturated SolutionUnsaturated Solution– more solute can still dissolve into solution more solute can still dissolve into solution

(less than solubility)(less than solubility)

• Supersaturated SolutionSupersaturated Solution– too much solute in solution-some will fall out too much solute in solution-some will fall out

(more than solubility)(more than solubility)

• We express the We express the quantitative amountquantitative amount of of solute in a solution with solute in a solution with concentrationconcentration … …

Solid-LiquidSolid-Liquid solubility with solubility with temperaturetemperature

BackBack

Bires, 2005 Slide 26

Solubility Graph PracticeSolubility Graph Practice

Work on the front side— 15 minutesWork on the front side— 15 minutes

Work on the back side- 15 minutesWork on the back side- 15 minutes

BackBack

Bires, 2005 Slide 27

KNO3 LabKNO3 Lab

BackBack

Bires, 2005 Slide 28

Warm UpWarm Up

Concentration - Concentration - MolarityMolarity• The “Stoichiometry” of SolutionsThe “Stoichiometry” of Solutions

• ConcentrationConcentration– the the quantitativequantitative amount of solute present in amount of solute present in

a solutiona solution

• MolarityMolarity ( (MM) – ) – moles/litermoles/liter– number of moles solute in liters of solutionnumber of moles solute in liters of solution

)(

)()(

Lsolutionofvolume

molsoluteofamountMMolarity

Try these Molarity questionsTry these Molarity questions• What is the concentration [in Molarity] when 3 What is the concentration [in Molarity] when 3

moles of NaCl are dissolved in 2 Liters of water?moles of NaCl are dissolved in 2 Liters of water?

• How much (in liters) of a 0.1 M solution do you How much (in liters) of a 0.1 M solution do you need to get 2 moles of solute?need to get 2 moles of solute?

• How many moles of NaOH are present in 300mL How many moles of NaOH are present in 300mL of a 1M solution?of a 1M solution?

• How many grams of HCl are found in 100mL of How many grams of HCl are found in 100mL of a 2M solution?a 2M solution?

1.5 M “molar”

20 L

.3 moles

7.2 grams

Solution PreparationSolution PreparationBy solid dissolving:By solid dissolving:1. Calculate how many grams are needed to 1. Calculate how many grams are needed to create our volume of our desired molarity create our volume of our desired molarity solutionsolution

2. Weigh out that mass, and add it to a 2. Weigh out that mass, and add it to a volumetric flaskvolumetric flask

3. add some water and allow to dissolve3. add some water and allow to dissolve

4. add water to the desired volume4. add water to the desired volume

BackBack

Bires, 2005 Slide 32

Solution PreparationSolution PreparationBy By dilutiondilution of a standard solution: of a standard solution:

1.1.Use the relationship Use the relationship MM11VV11==MM22VV22

2. Calculate volume of the 2. Calculate volume of the ““standard solution”standard solution” to use to get to use to get desired volume of desired volume of desired molarity desired molarity solutionsolution..

BackBack

Bires, 2005 Slide 33

Solution FormationSolution Formation• The nature of the solvent and solute The nature of the solvent and solute

affects whether a substance will dissolveaffects whether a substance will dissolve

• Other factors determine how fast a Other factors determine how fast a soluble substance dissolvessoluble substance dissolves– Agitation (shaking)Agitation (shaking)– TemperatureTemperature– Solute particle sizeSolute particle size

Will it dissolve? (Solubility Will it dissolve? (Solubility Rules)Rules)

• Not all ionic solids (salts) will dissolve.Not all ionic solids (salts) will dissolve.

• We use We use solubility rulessolubility rules to decide if the to decide if the substance will dissolve.substance will dissolve.

• Salts containingSalts containing……

1.1. Alkali metal cations Alkali metal cations (+) are (+) are solublesoluble..

2.2. NHNH44++, , NONO33

--, , SOSO442-2- are are solublesoluble..

3.3. PbPb++, , AgAg++, , HgHg2+2+ are are insolubleinsoluble..

4.4. COCO33--, , POPO44

3-3-, , SS2-2- are are insolubleinsoluble..

• Which of the following salts are soluble?Which of the following salts are soluble?

• NaCl, HgCONaCl, HgCO33, Ca(NO, Ca(NO33))22, AgF, PbI, AgF, PbI22, FeSO, FeSO44

BaSO4, SrSO4, and PbSO4 are insoluble

DissociationDissociation and Ions Present and Ions Present• DissociationDissociation = a salt dissolving into its = a salt dissolving into its

ions:ions:

• How many moles of ions are in a solution How many moles of ions are in a solution of 1 mole of NaCl?of 1 mole of NaCl?

• How many moles of ions are in solutions How many moles of ions are in solutions of 1 mole of each of the following?:of 1 mole of each of the following?:

)()()( aqaqs ClNaNaCl

24

24 SOCuCuSO

2332 2 CONaCONa

32

23 2)( NOMgNOMg

Net Ionic EquationsNet Ionic Equations• When we write a When we write a balanced chemical balanced chemical

equationequation, we show all species present (all , we show all species present (all reactants and all products):reactants and all products):

• In a In a net ionic equationnet ionic equation, we show only , we show only precipitates formed, and the reactants precipitates formed, and the reactants that form them:that form them:

• The chemicals that The chemicals that stay ionsstay ions are called are called spectator ionsspectator ions, , And are left outAnd are left out ( (NaNa++, , NONO33

--))

)(3)()()(3 aqsaqaq NaNOAgClNaClAgNO

)()()( saqaq AgClClAg Remember to Balance

Net Ionic Equation PracticeNet Ionic Equation Practice• Write the net ionic equations for the Write the net ionic equations for the

following:following: )()( )()(23 ntdisplacemedoubleKINOPb aqaq

)()(2)(2 ntdisplacemedoubleSKNiCl aqaq

)()(32)(2 ntdisplacemedoubleCONaBaCl aqaq

)(2)()(2

saqaq PbIIPb

)()(2

)(2

saqaq NiSSNi

)(3)(23)(

2saqaq BaCOCOBa

Strong/Weak ElectrolytesStrong/Weak Electrolytes• Recall that a solid compound made up of Recall that a solid compound made up of

a a cationcation and and anionanion is called a is called a saltsalt..

• SaltsSalts that that dissolve completelydissolve completely into their into their ions when put in water ions when put in water dissociate dissociate completelycompletely..

• Salts that Salts that dissociate completelydissociate completely form form strong electrolytesstrong electrolytes – solutions that – solutions that conduct electricity wellconduct electricity well..

• Some salts only Some salts only partially dissociatepartially dissociate, , forming forming weak electrolytesweak electrolytes – solutions that – solutions that conduct electricity, but do so poorlyconduct electricity, but do so poorly..