I. The Nature of Solutions Solutions. Mixtures Review Homogeneous –Solutions Heterogeneous –Suspension - is a fluid containing solid particles that.

I. The Nature of I. The Nature of SolutionsSolutions

SolutionsSolutions

Mixtures ReviewMixtures Review HomogeneousHomogeneous

– SolutionsSolutions HeterogeneousHeterogeneous

– SuspensionSuspension - is a fluid containing solid particles - is a fluid containing solid particles that are sufficiently large enough to settle.that are sufficiently large enough to settle.

– ColloidColloid - is a substance microscopically dispersed - is a substance microscopically dispersed evenly throughout another substance. Colloid evenly throughout another substance. Colloid particles are large enough to scatter light, this is particles are large enough to scatter light, this is called the called the Tyndall effectTyndall effect. The Tyndall effect is . The Tyndall effect is used to distinguish between a colloid and a solution. used to distinguish between a colloid and a solution.

– EmulsionEmulsion - is a mixture of two or more - is a mixture of two or more immiscibleimmiscible (un-blendable) liquids.(un-blendable) liquids.

SolutionsSolutions

Solution - Solution - homogeneous mixturehomogeneous mixture

Solvent Solvent - present in - present in greater amountgreater amount

Solute Solute - substance - substance being dissolvedbeing dissolved

SolutionsSolutions

Solute Solute - KMnO- KMnO44 Solvent Solvent - H- H22OO

SolvationSolvation

Solvation – Solvation – the process of dissolvingthe process of dissolving

solute particles are separated solute particles are separated and pulled into solutionand pulled into solution

solute particles are surrounded solute particles are surrounded by solvent particlesby solvent particles

B. SolvationB. Solvation

StrongElectrolyte

Non-Electrolyte

solute exists asions only

- +

salt

- +

sugar

solute exists asmolecules

only

- +

acetic acid

WeakElectrolyte

solute exists asions and

molecules DISSOCIATION IONIZATION

View animation online.

SolubilitySolubility

Soluble – substance can dissolve in a Soluble – substance can dissolve in a solvent solvent Ex: salt in waterEx: salt in water

Insoluble – substance cannot dissolve Insoluble – substance cannot dissolve in a solvent in a solvent

EEx: sand in waterx: sand in water

““like dissolves like”like dissolves like”

rule used to determine if substance rule used to determine if substance will dissolve in anotherwill dissolve in another

based on attractive forces between based on attractive forces between solute and solventsolute and solvent

““like dissolves like”like dissolves like”

polar solvents – dissolve polar polar solvents – dissolve polar molecular compounds and ionic molecular compounds and ionic compoundscompounds

ex: salt and water, alcohol and ex: salt and water, alcohol and vinegarvinegar

nonpolar solvents – dissolve nonpolar solvents – dissolve nonpolar compoundsnonpolar compounds

ex: oil and gasolineex: oil and gasoline

B. SolvationB. Solvation

NONPOLAR

NONPOLAR

POLAR

POLAR

““Like Dissolves Like”Like Dissolves Like”““Like Dissolves Like”Like Dissolves Like”

Factors Affecting Rate of SolvationFactors Affecting Rate of Solvation

How can you dissolve something How can you dissolve something faster?faster?

a)a) increase temp of solventincrease temp of solventthis accelerates particles creating this accelerates particles creating more particle collisionsmore particle collisions

The higher the temperature, higher the The higher the temperature, higher the solubility (solubility (for most cases)for most cases)

Factors Affecting Rate of SolvationFactors Affecting Rate of Solvation

b)b) agitate the solutionagitate the solution

more particle collisions between more particle collisions between solute and solventsolute and solvent

c)c) Increase surface area of soluteIncrease surface area of solute

breaking into smaller pieces allows breaking into smaller pieces allows more solute to be in contact with more solute to be in contact with solventsolvent

Heats of SolutionHeats of Solution Formation of a solution is accompanied by Formation of a solution is accompanied by

an energy change. an energy change.

The formation of a liquid-solid solution can The formation of a liquid-solid solution can absorb or release heat. absorb or release heat.

Solvent molecules are held together by Solvent molecules are held together by IMF, solvent-solvent attraction.IMF, solvent-solvent attraction.

Solute molecules are also held together by Solute molecules are also held together by IMF, solute-solute attraction.IMF, solute-solute attraction.

Heats of SolutionHeats of Solution Energy is required to separate these Energy is required to separate these

molecules in order for solvation to occur.molecules in order for solvation to occur.

Heat of Solution is the net amount of heat Heat of Solution is the net amount of heat energy absorbed or released when a energy absorbed or released when a specific amount of solute dissolves in a specific amount of solute dissolves in a solvent.solvent.

Heat of solution is negative when heat is Heat of solution is negative when heat is released and positive when heat is released and positive when heat is absorbed. absorbed.

SolubilitySolubility

maximum amount of solute that can maximum amount of solute that can dissolve in a solvent at a specific dissolve in a solvent at a specific temperaturetemperature

how much solute can be put into how much solute can be put into solvent?solvent?

Unsaturated SolutionUnsaturated Solution

less than maximum amount of solute less than maximum amount of solute dissolveddissolved

Ex. Ex. if I put sugar into water and all if I put sugar into water and all sugar is dissolved, solution is sugar is dissolved, solution is unsaturatedunsaturated

Saturated SolutionSaturated Solution

contains maximum amount of solute contains maximum amount of solute dissolveddissolved

Ex: Ex: if I put sugar into water and not if I put sugar into water and not dissolves (you can see the sugar), dissolves (you can see the sugar), the solution is saturatedthe solution is saturated

Supersaturated SolutionSupersaturated Solution contains more solute than a saturated contains more solute than a saturated

solution at the same conditionssolution at the same conditions

Ex: Ex: a saturated solution made at high a saturated solution made at high temp cools slowly. Slow cooling allows temp cools slowly. Slow cooling allows excess solute to remain dissolved in excess solute to remain dissolved in solution at lower temperaturesolution at lower temperature

very unstablevery unstable

SolubilitySolubility

SATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

concentration

SolubilitySolubility

SolubilitySolubility– maximum grams of solute that will maximum grams of solute that will

dissolve in 100 g of solvent at a given dissolve in 100 g of solvent at a given temperaturetemperature

– varies with tempvaries with temp– based on a saturated solutionbased on a saturated solution

SolubilitySolubility

Solubility Solubility CurveCurve– shows the shows the

dependence of dependence of solubility on solubility on temperaturetemperature

Solubility CurveSolubility Curve

Saturated-Saturated-Line Line represents represents max amount max amount solute that solute that will dissolve will dissolve at a given at a given temperaturetemperature

Temperature

Solu

bili

ty(g

solu

te/

10

0 g

H2O

)

Unsaturated(below line)

Supersaturated(above line)

SolubilitySolubility

Solids are more soluble at...Solids are more soluble at...– high temperatures.high temperatures.

Gases are more soluble at...Gases are more soluble at...– low temperatures &low temperatures &– high pressures (Henry’s Law).high pressures (Henry’s Law).– EXEX: soda: soda

Henry’s LawHenry’s Law

Henry's Law states that the mass of Henry's Law states that the mass of a gas which will dissolve into a a gas which will dissolve into a solution is directly proportional to the solution is directly proportional to the partial pressure of that gas above partial pressure of that gas above the solution. the solution.

Applies to gas-liquid solutions at Applies to gas-liquid solutions at constant temperatureconstant temperature

Solubility RulesSolubility Rules

Solubility is a result of an interaction Solubility is a result of an interaction between polar water molecules and between polar water molecules and the ions which make up a crystal.the ions which make up a crystal.

These two forces determine the These two forces determine the extent to which solution will occur.extent to which solution will occur.

Solubility RulesSolubility Rules

It is difficult to quantify how these two It is difficult to quantify how these two forces will work together. forces will work together.

Therefore, we refer to a set of Therefore, we refer to a set of generalizations about solubilitygeneralizations about solubility

These are called 'solubility rules', These are called 'solubility rules',

These rules are based upon These rules are based upon experimentation. experimentation.

Solubility RulesSolubility Rules NONO33- - All nitrates are soluble. - - All nitrates are soluble.

ClCl-- - All chlorides are soluble except AgCl, Hg - All chlorides are soluble except AgCl, Hg22ClCl22, and PbCl, and PbCl22. .

(SO(SO44))22-- - Most sulfates are soluble. Exceptions include - Most sulfates are soluble. Exceptions include

BaSOBaSO44, PbSO, PbSO44, and SrSO, and SrSO44. .

(CO(CO33))22-- - All carbonates are insoluble except NH - All carbonates are insoluble except NH44

++ and those and those of the Group 1 elements. of the Group 1 elements.

OHOH-- - All hydroxides are insoluble except those of the Group - All hydroxides are insoluble except those of the Group 1 elements, Ba(OH)1 elements, Ba(OH)22, and Sr(OH), and Sr(OH)22. Ca(OH). Ca(OH)22 is slightly is slightly soluble. soluble.

SS22-- - All sulfides are insoluble except those of the Group 1 - All sulfides are insoluble except those of the Group 1

and Group 2 elements and NHand Group 2 elements and NH44++..

II. ConcentrationII. Concentration

SolutionsSolutions

Solution ConcentrationSolution Concentration

Concentration – how much solute Concentration – how much solute dissolved in amount of solventdissolved in amount of solvent

what is difference between what is difference between concentrated and diluted?concentrated and diluted?

Concentrated vs. DiluteConcentrated vs. Dilute

What is different between the What is different between the glasses of Kool-aid?glasses of Kool-aid?

Solution concentration can be Solution concentration can be described generallydescribed generally

DiluteDilute - reduced in strength, weak, - reduced in strength, weak, watered down.watered down.

ConcentratedConcentrated – stronger, pure. Has – stronger, pure. Has less water. less water.

What is the problem with What is the problem with just just using using dilute dilute and and concentratedconcentrated as descriptions of the as descriptions of the solution concentration?solution concentration?

Is solution B dilute or concentrated? Is solution B dilute or concentrated?

The terms dilute and concentrated The terms dilute and concentrated are relative.are relative.

Scientists need a more precise way Scientists need a more precise way of referring to the concentration of a of referring to the concentration of a solution. solution.

Concentrated Dilute

Solution A Solution B Solution C

ConcentrationConcentration

The amount of solute in a solution.The amount of solute in a solution.

Describing ConcentrationDescribing Concentration– % by mass% by mass - medicated creams - medicated creams

– % by volume% by volume - rubbing alcohol - rubbing alcohol

– ppm, ppbppm, ppb - water contaminants - water contaminants

– molaritymolarity - used by chemists - used by chemists

– molality molality - used by chemists- used by chemists

MolarityMolarity

The ratio of the moles of solute to The ratio of the moles of solute to the volume of solvent in liters.the volume of solvent in liters.

Molarity (M) = Moles of solute

Volume in Liters of Solvent

How to read MolarityHow to read Molarity 6.0 M NaCl6.0 M NaCl

Read: “6 molar solution of NaCl”Read: “6 molar solution of NaCl”

Can be abbreviated 6M solution Can be abbreviated 6M solution

You must be careful to label the You must be careful to label the molarity with a capital M so that it is molarity with a capital M so that it is not confused with not confused with mm for molality. for molality.

Types of Calculations with Molarity:Types of Calculations with Molarity:

1. Finding concentration of a solution.1. Finding concentration of a solution.

2. Finding the mass of solute needed.2. Finding the mass of solute needed.

3. Finding the volume of solution made.3. Finding the volume of solution made.

Finding ConcentrationFinding Concentration

Antifreeze is a solution of ethylene glycol, Antifreeze is a solution of ethylene glycol, CC22HH66OO22 in water. If 4.50 L of antifreeze in water. If 4.50 L of antifreeze contains 27.5 g of ethylene glycol, what is contains 27.5 g of ethylene glycol, what is the concentration of the solution? the concentration of the solution?

27.5 g C2H6O2

62.08 g C2H6O2

1 mol C2H6O2

4.5 L

= 0.0984 mol/L or

0.0984 M C2H6O2

Finding Mass Finding Mass

What mass of sodium carbonate, What mass of sodium carbonate, NaNa22COCO33, is present in 50 ml of a , is present in 50 ml of a 0.750M solution? 0.750M solution? 50 ml 1 L

1000 mL

0.750 mol

1 L 1 mol Na2CO3

105.99 g Na2CO3

= 3.97 g Na2CO3

Conversion Factor

Finding VolumeFinding Volume

What volume of 1.50 mol/L HCl What volume of 1.50 mol/L HCl solution contains 10.0 g of hydrogen solution contains 10.0 g of hydrogen chloride? chloride? 10.0 g HCl 1 mol HCl

36.46 g HCl 1.50 mol

1 L

= 0.183 L or 183 mL

Conversion Factor

Molarity Practice

Problems

Practice ProblemsPractice Problems

1. 1. A 0.750 L aqueous solution contains 90.0 A 0.750 L aqueous solution contains 90.0 g of ethanol, Cg of ethanol, C22HH55OH. Calculate the molar OH. Calculate the molar

concentration of the solution in mol·Lconcentration of the solution in mol·L-1-1..

Practice ProblemPractice Problem

2. What mass of NaCl are dissolved in 152 2. What mass of NaCl are dissolved in 152 mL of a solution if the concentration of the mL of a solution if the concentration of the solution is 0.364 M?solution is 0.364 M?

Practice ProblemPractice Problem

3. What mass of dextrose, C3. What mass of dextrose, C66HH1212OO66 is is dissolved in 325 mL of 0.258 M solution?dissolved in 325 mL of 0.258 M solution?

Practice ProblemPractice Problem

4. A mass of 98 g of sulfuric acid, 4. A mass of 98 g of sulfuric acid, HH22SOSO44, is dissolved in water to , is dissolved in water to prepare a 0.500 M solution. What is prepare a 0.500 M solution. What is the volume of the solution?the volume of the solution?

Practice ProblemPractice Problem

5. A solution of sodium carbonate, Na5. A solution of sodium carbonate, Na22COCO33, , contains 53.0 g of solute in 215 mL of contains 53.0 g of solute in 215 mL of solution. What is its molarity?solution. What is its molarity?

Practice ProblemPractice Problem

6. What is the molarity of a solution of 6. What is the molarity of a solution of HNO3 that contains 12.6 g of solute HNO3 that contains 12.6 g of solute in 5.00 L of solution?in 5.00 L of solution?

MolalityMolality

solvent ofkg

solute of moles(m)molality

mass of solvent onlymass of solvent only

1 kg water = 1 L water1 kg water = 1 L water

kg 1

mol0.25 0.25m

MolalityMolality

Find the molality of a solution containing Find the molality of a solution containing 75 g of MgCl75 g of MgCl22 in 250 mL of water. in 250 mL of water.

75 g MgCl75 g MgCl22 1 mol MgCl1 mol MgCl22

95.21 g MgCl95.21 g MgCl22

= = 3.23.2mm MgCl MgCl22

0.25 kg water0.25 kg water

kg

molm

MolalityMolality

How many grams of NaCl are req’d to make a How many grams of NaCl are req’d to make a 1.541.54mm solution using 0.500 kg of water? solution using 0.500 kg of water?

0.500 kg water0.500 kg water 1.54 mol NaCl1.54 mol NaCl

1 kg water1 kg water

= = 45.0 g NaCl45.0 g NaCl

58.44 g NaCl58.44 g NaCl

1 mol NaCl1 mol NaCl

kg 1

mol1.5 1.5m

2211 VMVM

DilutionDilution

Preparation of a desired solution by Preparation of a desired solution by adding water to a concentrate.adding water to a concentrate.

Moles of solute remain the same.Moles of solute remain the same.

DilutionDilution

What volume of 15.8What volume of 15.8MM HNO HNO33 is required to make is required to make 250 mL of a 6.0250 mL of a 6.0MM solution? solution?

GIVEN:

M1 = 15.8M

V1 = ?

M2 = 6.0M

V2 = 250 mL

WORK:

M1 V1 = M2 V2

(15.8M) V1 = (6.0M)(250mL)

V1 = 95 mL of 15.8M HNO3

Preparing SolutionsPreparing Solutions

500 mL of 1.54500 mL of 1.54MM NaClNaCl

500 mLwater

45.0 gNaCl

– mass 45.0 g of NaClmass 45.0 g of NaCl– add water until add water until totaltotal

volume is 500 mLvolume is 500 mL– mass 45.0 g of NaClmass 45.0 g of NaCl– add 0.500 kg of water add 0.500 kg of water

500 mLmark

500 mLvolumetric

flask

1.541.54mm NaCl in NaCl in 0.500 kg of water0.500 kg of water

Preparing SolutionsPreparing Solutions

250 mL of 6.0250 mL of 6.0MM HNO HNO33 by dilutionby dilution– measure 95 mL measure 95 mL

of 15.8of 15.8MM HNO HNO33

95 mL of15.8M HNO3

water for

safety

250 mL mark

– combine with water until combine with water until totaltotal volume is 250 mL volume is 250 mL

– Safety:Safety: “Do as you “Do as you oughtta, add the acid to the oughtta, add the acid to the watta!” watta!”

Colligative PropertiesColligative Properties

Colligative Properties of SolutionsColligative Properties of Solutions

Solutes affect the physical properties Solutes affect the physical properties of their solventsof their solvents

Colligative properties – properties Colligative properties – properties that depend only on the number of that depend only on the number of solute particles present, not their solute particles present, not their identityidentity

Ex: boiling point, freezing pointEx: boiling point, freezing point

ElectrolytesElectrolytes

Definition – substances that break up Definition – substances that break up (ionize) in water to produce ions; can (ionize) in water to produce ions; can conduct electricityconduct electricity

- consist of acids, bases, ionic - consist of acids, bases, ionic compoundscompounds

Ex: NaCl Ex: NaCl Na Na1+1+ + Cl + Cl1-1-

HH22SOSO44 2 H 2 H++ + SO + SO442-2-

NonelectrolytesNonelectrolytes

Definition – do not break up (ionize) Definition – do not break up (ionize) in water, they stay the same; do not in water, they stay the same; do not conduct electricityconduct electricity

- usually molecular/covalent - usually molecular/covalent compoundscompounds

Ex:Ex: sugar sugar CC66HH1212OO66 C C66HH1212OO66

ethanolethanol CC22HH55OH OH C C22HH55OHOH

Properties of WaterProperties of Water

Water is PolarWater is Polar Water is polar because Water is polar because

oxygen is a “bully” oxygen is a “bully” and does not share and does not share the electronsthe electrons..

Oxygen is negative Oxygen is negative with more electrons with more electrons and Hydrogen is and Hydrogen is positive with less positive with less electrons.electrons.

CohesionCohesion

Cohesion is the Cohesion is the attraction of the attraction of the same type of same type of molecules to each molecules to each other. other.

Water molecules Water molecules stick together and stick together and “hold hands” with “hold hands” with hydrogen bondshydrogen bonds

Water is the Universal SolventWater is the Universal Solvent

Water is polar and Water is polar and can dissolve both can dissolve both salts, sugars, and salts, sugars, and other molecules.other molecules.

AdhesionAdhesion

Adhesion is the Adhesion is the attraction of attraction of molecules between molecules between two differenttwo different substances. substances.

Example: The Example: The attraction of water attraction of water molecules to a molecules to a glass. glass.

AdhesionAdhesion

Adhesion causes the Adhesion causes the water molecules to water molecules to stick to the sides of stick to the sides of the graduated the graduated cylinder creating a cylinder creating a meniscusmeniscus. .

Adhesion causes Adhesion causes water to rise in a water to rise in a straw. straw.