Chapter 13-14: Mixtures and Aqueous Solutions

BackBack

Bires, 2005 Slide 1

Chapter 13-14:Chapter 13-14: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

BackBack

Bires, 2005 Slide 2

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 polarrelatively polar..

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

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

Dissolution of NaCl.mov

BackBack

Bires, 2005 Slide 3

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 dissolver)the dissolver)

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

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

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

solution

BackBack

Bires, 2005 Slide 4

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.

BackBack

Bires, 2005 Slide 5

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 solutesolute• Dispersing mediumDispersing medium – the – the solventsolvent..• 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 398…page 398…

BackBack

Bires, 2005 Slide 6

7 Types of Colloids7 Types of ColloidsPage 398

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

BackBack

Bires, 2005 Slide 7

The Tyndall EffectThe Tyndall Effect• TheThe Tyndall effect Tyndall effect allows us toallows us to distinguish distinguish

between solutions, colloids, and between solutions, colloids, and suspensionssuspensions..

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

• Light Light doesn’t pass throughdoesn’t pass through– the mixture is a the mixture is a suspension or a suspension or a

heterogeneous colloidheterogeneous colloid..

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

• Light Light passespasses, but the , but the beam can be seenbeam can be seen in in the mixturethe mixture– the mixture is a the mixture is a homogeneous colloidhomogeneous colloid

John Tyndall, Brittish, c1860

BackBack

Bires, 2005 Slide 8

ElectrolytesElectrolytes• ElectrolytesElectrolytes

– Solutions that Solutions that conduct electricityconduct electricity..

• Ionic solutionsIonic solutions are are electrolyteselectrolytes..

• Covalent solutionsCovalent solutions are are nonelectrolytesnonelectrolytes..

• 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 testerConductivity tester– 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.

Electrolytes.mov

BackBack

Bires, 2005 Slide 9

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 much solute will dissolve)(how much 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

• 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 gassesgasses in liquids! … in liquids! …

BackBack

Bires, 2005 Slide 10

Solid-LiquidSolid-Liquid and and Gas-LiquidGas-Liquid solubility with temperaturesolubility with temperature

BackBack


Gasses in liquidsGasses in liquids• In addition to cold In addition to cold

temperatures, temperatures, high high pressures increase pressures increase solubilitysolubility of gasses of gasses 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.

Henry's Law.mov

BackBack


Like Dissolves Like!Like Dissolves Like!• Some solvents are Some solvents are polarpolar, like magnets, having , like magnets, having

partialpartial negative and partial positive endsnegative and 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..

• ““Like dissolves like”Like 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?

BackBack


SaturationSaturation• Saturated SolutionSaturated Solution

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

• Unsaturated SolutionUnsaturated Solution– more solute can dissolve into solution (less more solute can dissolve into solution (less

than solubility)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 … …

BackBack


Concentration - Concentration - MolarityMolarity• 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

• We can use the We can use the T-chart methodT-chart method to find to find moles of solute present.moles of solute present.

)(

)()(

Lsolutionofvolume

molsoluteofamountMMolarity

BackBack


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

BackBack


Concentration - Concentration - MolalityMolality• MolalityMolality ( (mm) – ) – moles/kilogrammoles/kilogram – number of – number of

moles solute in kilogram of moles solute in kilogram of solventsolvent..

• molality is used less often, but is important molality is used less often, but is important when we discuss when we discuss colligative propertiescolligative properties

• Remember, where Molarity is “Remember, where Molarity is “per liter per liter solutionsolution”, molality is “”, molality is “per kilogram of per kilogram of solventsolvent””

)(

)()(

kgsolventofmass

molsoluteofamountmMolality

BackBack


Try these molality questionsTry these molality questions• What is the concentration in molality when 2 What is the concentration in molality when 2

moles of NaCl are dissolved in 4kg of water?moles of NaCl are dissolved in 4kg of water?

• How many moles of solute are present in 1 kg How many moles of solute are present in 1 kg of a 3 m solution?of a 3 m solution?

• What mass of water do you need to add to 4 What mass of water do you need to add to 4 moles of NaCl to make a 2 m solution?moles of NaCl to make a 2 m solution?

• What is the molality of a solution created by What is the molality of a solution created by dissolving 3.5 moles methanol in 340g of CCldissolving 3.5 moles methanol in 340g of CCl44..

.5 m “molal”

3 moles

2 kilograms

10.3 m

BackBack


Solution PreparationSolution Preparation• By 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

• By dilution of a standard solution:By dilution of a standard solution:• 1. use the relationship 1. use the relationship MM11VV11==MM22VV22

• 2. calculate volume of 2. calculate volume of standard molarity solutionstandard molarity solution to use to get desired volume of to use to get desired volume of desired molarity desired molarity solutionsolution.. End of chapter 13 Dillutions.mov

Solution Prep of CuSO4.mov

BackBack


Begin C14Begin C14:: Colligative Properties Colligative Properties• ““ColligativeColligative” means ” means depends on amountdepends on amount..

• A colligative property of a solution A colligative property of a solution depends on the amount of solute depends on the amount of solute dissolved in solution.dissolved in solution.

• Physical Properties of a solution change Physical Properties of a solution change because solute particles act like because solute particles act like impurities, impurities, getting in the waygetting in the way of solvent of solvent particles.particles.

• We add impurities to We add impurities to lower freezing lower freezing pointspoints, , increase boiling pointsincrease boiling points, or , or reduce reduce vapor pressurevapor pressure..

Ethyl glycol is added to water in your car’s radiator to increase water’s boiling point.

The more impurities, the greater the change

BackBack


Osmosis and Osmotic PressureOsmosis and Osmotic Pressure• Osmosis is the travel of a solvent Osmosis is the travel of a solvent from an from an

area of low concentration (high purity) to area of low concentration (high purity) to high concentration (low purity).high concentration (low purity).

• Examples of osmosis:Examples of osmosis:– A Cucumber placed in a conc. NaCl solution A Cucumber placed in a conc. NaCl solution

(brine) loses water, shrivels up, and becomes a (brine) loses water, shrivels up, and becomes a pickle.pickle.

– Limp carrots and celery, placed in water, become Limp carrots and celery, placed in water, become firm because water enters via osmosis.firm because water enters via osmosis.

From pure to impure

BackBack


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..

BackBack


HH++ / / OHOH-- IonsIons – – ((Acids and BasesAcids and Bases))

• When a When a HH++ ion is released into solution, a ion is released into solution, a HH33OO++ ion is produced, called ion is produced, called Hydronium ionHydronium ion..

• When a When a OH-OH- ion is produced, we call this a ion is produced, we call this a Hydroxide ionHydroxide ion..

• HydroniumHydronium ( (HH33OO++) and ) and HydroxideHydroxide ( (OHOH--) are ) are the fundamental ions involved in the fundamental ions involved in acid/baseacid/base chem.chem.

• AcidsAcids that dissociate completely, that dissociate completely, releasing releasing H+H+ ions form ions form strong electrolytesstrong electrolytes..

• BasesBases that dissociate completely that dissociate completely releasing releasing OH-OH- ions form ions form strong electrolytesstrong electrolytes..End of chapter 14 – Problem set on next

slide

Aqueous Acids (strong and weak).mov

Aqueous Bases (strong and weak).mov

ClHHCl

OHNaNaOH

BackBack


Chapter 14 Quiz Review Chapter 14 Quiz Review ProblemsProblems

• In your text, on page 447, do the In your text, on page 447, do the following (for a grade) as a quiz review:following (for a grade) as a quiz review:

• #1-2#1-2 : Solubility of salts : Solubility of salts

•#13-15#13-15 : Dissociation of aqueous salts : Dissociation of aqueous salts

• #16-18#16-18 : Precipitation reactions, net ionic : Precipitation reactions, net ionic equations, and spectator ionsequations, and spectator ions

Chapter 13-14: Mixtures and Aqueous Solutions

Documents

Transcript of Chapter 13-14: Mixtures and Aqueous Solutions