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AnnouncementsAnnouncements & Agenda& Agenda (02/14/07)(02/14/07)Happy Valentine’s Day!Happy Valentine’s Day!Please pick up your exams up front.Please pick up your exams up front.GOOD NEWSGOOD NEWS Exam average was a ~76% - Nice jobExam average was a ~76% - Nice job Decided we will allow you to replace a low test score Decided we will allow you to replace a low test score

with your final exam grade if it is higherwith your final exam grade if it is higher Starting next Wed - will hold an unofficial weekly review Starting next Wed - will hold an unofficial weekly review

@ 3pm, Room TBA@ 3pm, Room TBA

Agenda for the next 5 classes: Ch 7, Ch 8, & MovieAgenda for the next 5 classes: Ch 7, Ch 8, & Movie

TodayToday Exam DiscussionExam Discussion Solutions & Solution Properties (7.1-7.3)Solutions & Solution Properties (7.1-7.3) Solution Concentrations (7.4)Solution Concentrations (7.4)

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General ObservationsGeneral Observations

Nice class average (~76%) – nice job! Nice class average (~76%) – nice job!

Show as much work as possibleShow as much work as possible tried to give as much partial credit as I could…tried to give as much partial credit as I could…

Some struggles with quiz-like questionsSome struggles with quiz-like questions

Be sure you understand objectivesBe sure you understand objectives

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Exam 1 ResultsExam 1 Results

What to do if….?What to do if….? Go over the test – figure out what & Go over the test – figure out what &

why?why? Make a plan…Make a plan… Come visit me to evaluate your Come visit me to evaluate your

situation…situation…

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Test 1 was:Test 1 was:

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0%

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0% 1.1. About what I expectedAbout what I expected

2.2. A bit challenging, but doable if I studiedA bit challenging, but doable if I studied

3.3. Quite challenging – need to study moreQuite challenging – need to study more

4.4. Oh my!!! Time to talk to Bob…Oh my!!! Time to talk to Bob…

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For those who did well… What did For those who did well… What did you do to be successful?you do to be successful?

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0%

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0% 1.1. Solving problems, reviewing quizzesSolving problems, reviewing quizzes2.2. Reviewing lecturesReviewing lectures3.3. Reading the bookReading the book4.4. Working with somebody elseWorking with somebody else5.5. Just lots of time on all of the aboveJust lots of time on all of the above

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CHAPTER 7: SOLUTIONS!CHAPTER 7: SOLUTIONS!

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Nature of SolutionsNature of Solutions

SolutionSolution – homogeneous mixture of two or – homogeneous mixture of two or more substancesmore substances SolventSolvent – the main medium, present in the – the main medium, present in the

largest quantitylargest quantity SoluteSolute – material dissolved in the solvent – material dissolved in the solvent

They don’t just have to be liquids:They don’t just have to be liquids:

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Solutes areSolutes are• spread evenly spread evenly

throughout the throughout the solution. solution.

• cannotcannot be separated be separated by filtration. by filtration.

• cancan be separated by be separated by evaporation. evaporation.

• are not visible, but can are not visible, but can give a color to the give a color to the solution.solution.

Nature of Solutes in SolutionsNature of Solutes in Solutions

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Determination of SolubilityDetermination of Solubility

Definitions you may already know:Definitions you may already know:Solubility of solutes vary tremendously…Solubility of solutes vary tremendously…Miscible:Miscible: when two liquids mix in all proportions when two liquids mix in all proportions (Acetone and Water)(Acetone and Water)Immiscible:Immiscible: when two liquids DO NOT mix at all when two liquids DO NOT mix at all (Oil and water)(Oil and water)Insoluble:Insoluble: when a solid does not dissolve in a when a solid does not dissolve in a solvent (NaCl in gasoline)solvent (NaCl in gasoline)Saturated:Saturated: a solution that has dissolved the a solution that has dissolved the maximum possible solute maximum possible solute

REALITY IS USUALLY SOMEWHERE IN BETWEEN!REALITY IS USUALLY SOMEWHERE IN BETWEEN!

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Water: Nature’s SolventWater: Nature’s Solvent

• is a polar moleculeis a polar molecule• forms hydrogen bonds between the forms hydrogen bonds between the

hydrogen atom in one molecule and the hydrogen atom in one molecule and the oxygen atom in a different water molecule.oxygen atom in a different water molecule.

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Hydrogen Bonding ReminderHydrogen Bonding Reminder

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Formation of an Ionic SolutionFormation of an Ionic Solution

NaNa++ and Cl and Cl-- ions ions• on the surface of a on the surface of a

NaCl crystal are NaCl crystal are attracted to polar attracted to polar water molecules.water molecules.

• are hydrated in are hydrated in solution with many solution with many HH22O molecules O molecules

surrounding each ion.surrounding each ion.

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Solubility of SaltsSolubility of Salts

• Must overcome strong +/- love between ions of the salt (called lattice energy)• Solution (pun intended) to the problem: ion-dipole interactions – strength in numbers

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When NaCl(s) dissolves in water, the When NaCl(s) dissolves in water, the reaction can be written asreaction can be written as

HH22OO

NaCl(NaCl(ss) ) Na Na++((aqaq) + Cl) + Cl- - ((aqaq))

solid separation of ionssolid separation of ions

Equations for Solution FormationEquations for Solution Formation

This is reality in ionic solutions!!!This is reality in ionic solutions!!!

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““Like Dissolves Like”Like Dissolves Like”

What does this mean?What does this mean?Answer: compatibility of intermolecular Answer: compatibility of intermolecular forces (last week)forces (last week)Typically, compounds with similar polarity Typically, compounds with similar polarity will be soluble in each other.will be soluble in each other.Predicting trends based on properties…Predicting trends based on properties…

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Like Dissolves LikeLike Dissolves Like

SolventsSolvents

Water (polar)Water (polar)

CHCH22ClCl22(nonpolar)(nonpolar)

II2 2 (nonpolar)(nonpolar)

Ni(NONi(NO33))22

(polar)(polar)

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Which of the following solutes will dissolve in Which of the following solutes will dissolve in water? Why?water? Why?

1) Na1) Na22SOSO4 4

2) gasoline 2) gasoline

3) SiCl3) SiCl44

4) HCl4) HCl

ExampleExample

Yes, ionicYes, ionic

No, nonpolarNo, nonpolar

No, nonpolarNo, nonpolar

Yes, polarYes, polar

Most polar and ionic solutes dissolve in Most polar and ionic solutes dissolve in waterwater

because water is a polar solvent.because water is a polar solvent.

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Which of the following vitamins are fat-soluble Which of the following vitamins are fat-soluble and which are water soluble?and which are water soluble?

Vitamins: organic Vitamins: organic molecules required for molecules required for proper function but not proper function but not made by the body. made by the body. (Obtain by eating!)(Obtain by eating!)

2 categories: 2 categories:

fat-soluble (dissolve in fat-soluble (dissolve in fatty hydrocarbon-like fatty hydrocarbon-like tissues) tissues)

water-solublewater-soluble

Why we need at least some oil & fat in our diet!Why we need at least some oil & fat in our diet!

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Electrolytes & Nonelectrolytes (7.2)Electrolytes & Nonelectrolytes (7.2)

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In water, In water, • strong electrolytesstrong electrolytes produce ions and conduct an produce ions and conduct an

electric current. electric current. • weak electrolytesweak electrolytes produce a few ions. produce a few ions. • nonelectrolytesnonelectrolytes do not produce ions. do not produce ions.

Solutes and Ionic ChargeSolutes and Ionic Charge

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• dissociate in water producing + & – ionsdissociate in water producing + & – ions• conduct an electric currentconduct an electric current• in equations show the formation of ions in aqueous in equations show the formation of ions in aqueous

((aqaq) solutions.) solutions.

HH22O O 100% ions 100% ions

NaCl(NaCl(ss) ) Na Na++((aqaq) + Cl) + Cl−− ( (aqaq) )

HH22OO

CaBrCaBr22((ss)) Ca Ca2+2+((aqaq) + 2Br) + 2Br−− ( (aqaq))

Strong ElectrolytesStrong Electrolytes

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• dissociate only slightly in waterdissociate only slightly in water• in water forms a solution of a few ions and mostly in water forms a solution of a few ions and mostly

undissociated molecules.undissociated molecules.

HF(HF(g)g) + H + H22O(O(l)l) H H33OO++((aqaq) + F) + F-- ( (aqaq))

NHNH33((g)g) + H + H22O(O(l)l) NH NH44++((aqaq) + OH) + OH-- ( (aq)aq)

Weak ElectrolytesWeak Electrolytes

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NonelectrolytesNonelectrolytes

• dissolve as dissolve as molecules molecules

• do not produce ionsdo not produce ions• do not conduct an do not conduct an

electric currentelectric current

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Electrolytes in the BodyElectrolytes in the Body

Carry messages send to and from the Carry messages send to and from the

brain as electrical signalsbrain as electrical signals

Maintain cellular function with the correct Maintain cellular function with the correct

concentrations electrolytesconcentrations electrolytes

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Electrolyte balance in cells is importantElectrolyte balance in cells is important

KK++, Mg, Mg+2+2, X, X--

NaNa++, Ca, Ca2+2+, Cl, Cl--

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EquivalentsEquivalents

An equivalent (Eq) is the amount of an electrolyte An equivalent (Eq) is the amount of an electrolyte or an ion that provides 1 mole of electrical charge or an ion that provides 1 mole of electrical charge (+ or -).(+ or -).

1 mole Na1 mole Na++ = = 1 equivalent1 equivalent

1 mole Cl1 mole Cl−− = = 1 equivalent1 equivalent

1 mole Ca1 mole Ca2+2+ = = 2 equivalents2 equivalents

1 mole Fe1 mole Fe3+3+ = 3 equivalents= 3 equivalents

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Electrolytes in Body FluidsElectrolytes in Body Fluids

In replacement solutions for body fluids, the In replacement solutions for body fluids, the electrolytes are given in milliequivalents per liter electrolytes are given in milliequivalents per liter (mEq/L). (mEq/L).

Ringer’s SolutionRinger’s Solution

NaNa++ 147 mEq/L 147 mEq/L ClCl−− 155 mEq/L 155 mEq/L

KK++ 4 mEq/L 4 mEq/L

CaCa2+2+ 4 mEq/L 4 mEq/L

The milliequivalents per liter of cations must equal The milliequivalents per liter of cations must equal the milliequivalents per liter of anions. the milliequivalents per liter of anions.

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• the maximum amount of solute that the maximum amount of solute that dissolves in a specific amount of solvent. dissolves in a specific amount of solvent.

• expressed as grams of solute in 100 expressed as grams of solute in 100 grams of solvent water.grams of solvent water.

g of soluteg of solute

100 g water100 g water

Solubility & Concentration (7.3-7.4)Solubility & Concentration (7.3-7.4)

Unsaturated vs. Saturated SolutionsUnsaturated vs. Saturated Solutions

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At 40At 40C, the solubility of KBr is 80 g/100 g HC, the solubility of KBr is 80 g/100 g H22O.O.

Identify the following solutions as eitherIdentify the following solutions as either1) saturated or 2) unsaturated. Explain.1) saturated or 2) unsaturated. Explain.

A. 60 g KBr added to 100 g of water at 40A. 60 g KBr added to 100 g of water at 40C.C.

B. 200 g KBr added to 200 g of water at 40B. 200 g KBr added to 200 g of water at 40C.C.

C. 25 g KBr added to 50 g of water at 40C. 25 g KBr added to 50 g of water at 40C.C.

Learning CheckLearning Check

What happens to the “leftover” solute???What happens to the “leftover” solute???

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Effect of Temperature on SolubilityEffect of Temperature on Solubility

• Depends on Temp!Depends on Temp!

• Solids: usually Solids: usually increases as increases as temperature inc.temperature inc.

• Gases: usually Gases: usually decreases as decreases as temperature inc.temperature inc.

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Solubility and PressureSolubility and PressureHenry’s Law:Henry’s Law:

• Gas solubility is Gas solubility is directly related to directly related to gas pressure above gas pressure above the liquidthe liquid

• at higher pressures, at higher pressures, more gas molecules more gas molecules dissolve in the dissolve in the liquid.liquid.

Real life examples… soda, the bends, etc.

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

amount of soluteamount of solute

amount of solutionamount of solution

Comes in all sorts of fantastic flavors!Comes in all sorts of fantastic flavors!• Mass PercentMass Percent• Volume PercentVolume Percent• Mass/Volume PercentMass/Volume Percent• MolarityMolarity

Percent Concentration (7.4)Percent Concentration (7.4)

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• concentration is the percent by mass of concentration is the percent by mass of solute in a solution.solute in a solution.

mass percent = mass percent = g of solute g of solute x 100 x 100

g of solute + g of solventg of solute + g of solvent

• amount in g of solute in 100 g of solution.amount in g of solute in 100 g of solution.

mass percent = mass percent = g of solute g of solute x 100x 100

100 g of solution100 g of solution

Mass Percent (% m/m)Mass Percent (% m/m)

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Mass of SolutionMass of Solution

8.00 g KCl8.00 g KCl

50.00 g KCl 50.00 g KCl solutionsolution

Add water to Add water to give 50.00 g give 50.00 g solutionsolution

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Calculation of mass percent (% m/m) requires theCalculation of mass percent (% m/m) requires the

• grams of solute (g KCl) andgrams of solute (g KCl) and

• grams of solution (g KCl solution).grams of solution (g KCl solution).

g of KCl g of KCl = = 8.00 g 8.00 g

g of solvent (water) g of solvent (water) = = 42.00 g42.00 g

g of KCl solution g of KCl solution = = 50.00 g50.00 g

8.00 g KCl (solute) 8.00 g KCl (solute) x 100 = 16.0% (m/m) x 100 = 16.0% (m/m)

50.00 g KCl solution50.00 g KCl solution

Calculating Mass PercentCalculating Mass Percent

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• percent volume (mL) of solute (liquid) to volume percent volume (mL) of solute (liquid) to volume (mL) of solution.(mL) of solution.

volume % (v/v) = volume % (v/v) = mL of solute mL of solute x 100 x 100 mL of solution mL of solution

• solute (mL) in 100 mL of solution.solute (mL) in 100 mL of solution.

volume % (v/v) = volume % (v/v) = mL of solute mL of solute 100 mL of solution 100 mL of solution

Volume Percent (% v/v)Volume Percent (% v/v)

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• percent mass (g) of solute to volume (mL) of percent mass (g) of solute to volume (mL) of solution.solution.

mass/volume % (m/v) = mass/volume % (m/v) = g of solute g of solute x x 100100 mL of solution mL of solution

• solute (g) in 100 mL of solution.solute (g) in 100 mL of solution.

mass/volume % (m/v) = mass/volume % (m/v) = g of solute g of solute x x 100 100 100 mL of solution 100 mL of solution

Mass/Volume Percent (% m/v)Mass/Volume Percent (% m/v)

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Percent Conversion FactorsPercent Conversion Factors

Two conversion factors can be written for Two conversion factors can be written for each type of % value.each type of % value.

TABLE 7.7

5% (m/v) glucose There are 5 g of glucose 5 g glucose and 100 mL solution

in 100 mL of solution. 100 mL solution 5 g glucose

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How many grams of NaOH are needed to How many grams of NaOH are needed to prepare 75.0 g of 14.0% (m/m) NaOH solution?prepare 75.0 g of 14.0% (m/m) NaOH solution?

0%

0%

0% 1) 10.5 g NaOH1) 10.5 g NaOH

2) 75.0 g NaOH2) 75.0 g NaOH

3) 536 g NaOH3) 536 g NaOH

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1)1)10.5 g NaOH10.5 g NaOH

75.0 g solution x 75.0 g solution x 14.0 g NaOH 14.0 g NaOH = 10.5 g = 10.5 g NaOHNaOH

100 g solution100 g solution

14.0% (m/m) factor14.0% (m/m) factor

SolutionSolution

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How many milliliters of a 5.75% (v/v) ethanol How many milliliters of a 5.75% (v/v) ethanol solution can be prepared from 2.25 mL ethanol?solution can be prepared from 2.25 mL ethanol?

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0%

0% 1) 2.56 mL1) 2.56 mL

2) 12.9 mL2) 12.9 mL

3) 39.1 mL3) 39.1 mL

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3) 39.1 mL 3) 39.1 mL

2.25 mL ethanol x 2.25 mL ethanol x 100 mL solution 100 mL solution 5.75 mL 5.75 mL

ethanolethanol

5.75% (v/v) inverted5.75% (v/v) inverted

= 39.1 mL solution= 39.1 mL solution

SolutionSolution