Chapter 12-13: Mixtures and Aqueous Solutions
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Transcript of Chapter 12-13: Mixtures and Aqueous Solutions
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..
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• 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..
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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
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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
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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..
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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.
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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??
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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
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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! …
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Reading Solubility CurvesReading Solubility Curves
Solid-LiquidSolid-Liquid solubility with solubility with temperaturetemperature
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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..
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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
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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
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KNO3 LabKNO3 Lab
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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
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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..
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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..