11

AnnouncementsAnnouncements & Agenda& Agenda (02/21/07)(02/21/07)

You should be reading Ch 8!You should be reading Ch 8!

Quiz on Friday: Ch 7 + TodayQuiz on Friday: Ch 7 + Today

Open Review/Problems @ 3pm Wed (Here!)Open Review/Problems @ 3pm Wed (Here!)

TodayToday Osmosis (7.7)Osmosis (7.7) What are acids & bases? (8.1, 8.2)What are acids & bases? (8.1, 8.2) Acid & base strength: Qualitative (8.3)Acid & base strength: Qualitative (8.3) Acid & base strength: Quantitative (8.4-8.5)Acid & base strength: Quantitative (8.4-8.5) Recommend: Do the Ch 8 CD tutorials!!!Recommend: Do the Ch 8 CD tutorials!!!

22

Last Time: Solubility & TemperatureLast Time: Solubility & Temperature

• 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.

33

Last Time: Solubility and PressureLast Time: Solubility and Pressure

Henry’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.Real life examples… soda, the bends, etc.

44

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

Last Time: ConcentrationLast Time: Concentration

55

Last Time: DilutionLast Time: DilutionIn the initial and diluted solution,In the initial and diluted solution,

• the amount of solute is the same.the amount of solute is the same.

• the concentrations and volumes are related by the the concentrations and volumes are related by the following equations:following equations:

For percent concentration:For percent concentration:

CC11VV11 = C = C22VV22

initial dilutedinitial diluted

For molarity:For molarity:

MM11VV11 = M = M22VV22

initial dilutedinitial diluted

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Last Time: OsmosisLast Time: Osmosis

• water (solvent) flows water (solvent) flows from the lower solute from the lower solute concentration into the concentration into the higher solute higher solute concentration. concentration.

• the level of the solution the level of the solution with the higher with the higher concentration rises.concentration rises.

• the concentrations of the concentrations of the 2 solutions become the 2 solutions become equal with time.equal with time.

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Osmotic PressureOsmotic Pressure

• produced by the solute particles dissolved in produced by the solute particles dissolved in a solution.a solution.

• equal to the pressure that would prevent the equal to the pressure that would prevent the flow of additional water into the more flow of additional water into the more concentrated solution.concentrated solution.

• greater as the number of dissolved particles greater as the number of dissolved particles in the solution increases.in the solution increases.

88

Osmotic Pressure of the BloodOsmotic Pressure of the Blood

Red blood cellsRed blood cells

• have cell walls that are semipermeable have cell walls that are semipermeable membranes.membranes.

• maintain an osmotic pressure that cannot maintain an osmotic pressure that cannot change or damage occurs. change or damage occurs.

• must maintain an equal flow of water must maintain an equal flow of water between the red blood cell and its between the red blood cell and its surrounding environment. surrounding environment.

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Isotonic SolutionsIsotonic Solutions

• exerts the same osmotic exerts the same osmotic pressure as red blood cells. pressure as red blood cells.

• is known as a “physiological is known as a “physiological solution”.solution”.

• of 5.0% glucose or 0.90% of 5.0% glucose or 0.90% NaCl is used medically NaCl is used medically because each has a solute because each has a solute concentration equal to the concentration equal to the osmotic pressure equal to osmotic pressure equal to red blood cells.red blood cells.

H2O

1010

Hypotonic SolutionsHypotonic Solutions

• has a lower osmotic has a lower osmotic pressure than red blood pressure than red blood cells.cells.

• has a lower has a lower concentration than concentration than physiological solutions. physiological solutions.

• causes water to flow into causes water to flow into red blood cells.red blood cells.

• causes hemolysis: RBCs causes hemolysis: RBCs swell and may burst.swell and may burst.

H2O

1111

Hypertonic SolutionsHypertonic Solutions

• has a higher osmotic has a higher osmotic pressure than RBCs.pressure than RBCs.

• has a higher has a higher concentration than concentration than physiological physiological solutions. solutions.

• causes water to flow causes water to flow out of RBCs.out of RBCs.

• cause crenation: cause crenation: RBCs shrinks in size.RBCs shrinks in size.

H2O

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DialysisDialysis

In In dialysisdialysis,,

• solvent and small solute particles pass solvent and small solute particles pass through an artificial membrane.through an artificial membrane.

• large particles are retained inside.large particles are retained inside.

• waste particles such as urea from blood are waste particles such as urea from blood are removed using hemodialysis (artificial removed using hemodialysis (artificial kidney). kidney).

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Chapter 8: Acids and BasesChapter 8: Acids and Bases

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25 Good Practice Problems (Ch 8)25 Good Practice Problems (Ch 8)

11 22 33 44 55

8.01, 8.05, 8.07, 8.09, 8.11, 8.13, 8.01, 8.05, 8.07, 8.09, 8.11, 8.13, 8.15, 8.17, 8.19, 8.23, 8.25, 8.27, 8.15, 8.17, 8.19, 8.23, 8.25, 8.27, 8.33, 8.37, 8.41, 8.43, 8.45, 8.47, 8.33, 8.37, 8.41, 8.43, 8.45, 8.47, 8.49, 8.55, 8.61, 8.65, 8.67, 8.69, 8.49, 8.55, 8.61, 8.65, 8.67, 8.69, 8.718.71

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AcidsAcids

Arrhenius acidsArrhenius acids • produce Hproduce H++ ions in water. ions in water.

HH22OOHHCl(Cl(gg) ) HH++((aqaq) + Cl) + Cl- - ((aqaq))

• are electrolytes.are electrolytes.• have a sour taste.have a sour taste.• May sting May sting • turn litmus (pH paper) red.turn litmus (pH paper) red.• neutralize bases. neutralize bases.

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BasesBases

Arrhenius basesArrhenius bases • produce OHproduce OH−− ions in ions in

water.water.• taste bitter or chalky.taste bitter or chalky.• are electrolytes.are electrolytes.• feel soapy and feel soapy and

slippery.slippery.• neutralize acids. neutralize acids.

1717

BrBroonsted-Lowry Acids and Basesnsted-Lowry Acids and Bases

Another theory: the BrAnother theory: the BrØØnsted-Lowry theory…nsted-Lowry theory…• acids donate a proton (Hacids donate a proton (H++) ) • bases accept a proton (Hbases accept a proton (H++))

1818

NHNH33, a Br, a BrØØnsted-Lowry Basensted-Lowry Base

In the reaction of ammonia and water,In the reaction of ammonia and water,

• NHNH33 is the base that accept H is the base that accept H++..

• HH22O is the acid that donates HO is the acid that donates H++..

1919

• A A strong acid/basestrong acid/base completely ionizes (100%) completely ionizes (100%) in aqueous solutions.in aqueous solutions.

HCl(HCl(gg) + H) + H22O(O(ll) H) H33OO++ ( (aqaq) + Cl) + Cl−− ( (aqaq))

COMPARE TO STRONG ELECTROLYTESCOMPARE TO STRONG ELECTROLYTES

• A A weak acid/baseweak acid/base dissociates only slightly in dissociates only slightly in water to form a few ions in aqueous solutions. water to form a few ions in aqueous solutions.

HH22COCO33((aqaq) + H) + H22O(O(ll) H) H33OO++((aqaq) + HCO) + HCO33−− ( (aqaq))

COMPARE TO WEAK ELECTROLYTESCOMPARE TO WEAK ELECTROLYTES

Strengths of Acids/Bases: IonizationStrengths of Acids/Bases: Ionization

2020

• make up six (just a few) of all the acids. make up six (just a few) of all the acids.

• have weak conjugate bases (the product have weak conjugate bases (the product formed after the proton is transferred).formed after the proton is transferred).

Strong Acids (Know These)Strong Acids (Know These)

2121

Strong BasesStrong Bases

• are formed from metals of are formed from metals of Groups 1A (1) and 2A (2). Groups 1A (1) and 2A (2).

• include LiOH, NaOH, KOH, include LiOH, NaOH, KOH, and Ca(OH)and Ca(OH)22..

• dissociate completely in water.dissociate completely in water.

KOH(KOH(ss) K) K++((aqaq) + OH) + OH−−((aqaq))

2222

Weak AcidsWeak Acids

• only a few molecules only a few molecules dissociate.dissociate.

• most of the weak acid most of the weak acid remains as the remains as the undissociated (molecular) undissociated (molecular) form of the acid.form of the acid.

• the concentrations of the the concentrations of the HH33OO+ +

and the anion (Aand the anion (A--) are ) are small.small. HA(aq) + H2O(l) H3O(aq) + A−(aq)

2323

Weak AcidsWeak Acids

• make up most of the acids. make up most of the acids. • have relatively strong conjugate bases.have relatively strong conjugate bases.

2424

NHNH33((gg) + H) + H22O(O(ll) NH) NH44++((aqaq) + OH) + OH−−((aqaq))

Weak BasesWeak Bases

• dissociate only slightly in dissociate only slightly in

water.water.

• form only a few ions in form only a few ions in

water.water.

2525

In water In water occasionallyoccasionally,,• HH++ is transferred from 1 H is transferred from 1 H22O molecule to another. O molecule to another. • one water acts an acid, the another acts as a base.one water acts an acid, the another acts as a base.

HH22O + HO + H22O HO H33OO++ + OH+ OH−− .. .. .. .. .. .. .... ::OO:: H + H + HH::OO:: H H::OO::HH ++ + + ::OO::HH−−

.. .. .. .. .. .. .... HH HH H H water water hydronium hydroxidewater water hydronium hydroxide

ion (+)ion (+) ion (-)ion (-)

Ionization of Water: A Basis for Ionization of Water: A Basis for Understanding pH (H+ concentrations)Understanding pH (H+ concentrations)

2626

Pure Water is Neutral Pure Water is Neutral (NOT ACIDIC OR BASIC)(NOT ACIDIC OR BASIC)

• the ionization of water the ionization of water molecules produces small, molecules produces small, but equal quantities of Hbut equal quantities of H33OO++

and OHand OH−− ions.ions.• molar concentrations are molar concentrations are

indicated in brackets as indicated in brackets as [H[H33OO++] and [OH] and [OH−−]. ].

[H[H33OO++]] = 1.0 x 10= 1.0 x 10−−7 7 MM

[OH[OH−−]] == 1.0 x 101.0 x 10−−7 7 MM

2727

Acidic SolutionsAcidic Solutions

Adding an acid to Adding an acid to pure water:pure water:

• increases the increases the [H[H33OO++].].

• causes the causes the [H[H33OO++]] to to

exceed 1.0 x 10exceed 1.0 x 10-7 -7 M.M.

• decreases the decreases the [OH[OH−−].].

2828

Basic SolutionsBasic Solutions

Adding a base to pure Adding a base to pure water:water:

• increases the increases the [OH[OH−−].].

• causes the causes the [OH[OH−−]] to to exceed 1.0 x 10exceed 1.0 x 10−− 7 7M.M.

• decreases the decreases the [H[H33OO++].].

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

2929

The ion product constant, KThe ion product constant, Kww, for water , for water

• is the product of the concentrations of the hydronium is the product of the concentrations of the hydronium and hydroxide ions.and hydroxide ions.

KKww = = [ H[ H33OO++]] [ OH[ OH−− ]]

• can be obtained from the concentrations in pure water.can be obtained from the concentrations in pure water.

KKww = = [ H[ H33OO++]] [ OH[ OH−− ]]

KKww = [1.0 x 10 = [1.0 x 10−− 7 7 M] x [ 1.0 x 10M] x [ 1.0 x 10−− 7 7 M] M]

= = 1.0 x 101.0 x 10−− 14 14

Ion Product of Water, KIon Product of Water, Kww

3030

[H[H33OO++] and [OH] and [OH−−] in Solutions] in Solutions

IMPORTANT: Kw is always 1.0 x 10−14.

3131

Calculating [HCalculating [H33OO++]]What is the [HWhat is the [H33OO++] of a solution if [OH] of a solution if [OH−−] is 5.0 x 10] is 5.0 x 10-8-8

M? M?

STEP 1:STEP 1: Write the K Write the Kww for water. for water.

KKww = [H = [H33OO+ + ][OH][OH−− ] = 1.0 x 10] = 1.0 x 10−−1414

STEP 2:STEP 2: Rearrange the K Rearrange the Kww expression. expression.

[H[H33OO++] = ] = 1.0 x 101.0 x 10-14-14

[OH[OH−−]]

STEP 3:STEP 3: Substitute [OH Substitute [OH−−].]. [H[H33OO++] = ] = 1.0 x 101.0 x 10-14 -14 = 2.0 x 10= 2.0 x 10-7-7 M M

5.0 x 105.0 x 10- 8 - 8

3232

If lemon juice has [HIf lemon juice has [H33OO++] of 2 x 10] of 2 x 10−−33 M, what M, what

is the [OHis the [OH−−] of the solution?] of the solution?

1) 1) 2 x 102 x 10−−1111 M M

2) 2) 5 x 105 x 10−−1111 M M

3) 3) 5 x 105 x 10−−1212 M M

11 22 33 44 55 66 77 88 99 1010 1111 1212 1313 1414 1515 1616 1717 1818 1919 2020

2121 2222 2323 2424 2525 2626 2727 2828 2929 3030 3131 3232 3333 3434 3535 3636 3737 3838 3939 4040

4141 4242 4343 4444 4545 4646 4747 4848 4949 5050 5151 5252 5353 5454 5555 5656 5757 5858 5959 6060

6161 6262 6363 6464 6565 6666 6767 6868 6969 7070 7171 7272 7373 7474 7575

3333

3) 3) 5 x 105 x 10−−1212 M M

Rearrange the KRearrange the Kww to solve for [OH to solve for [OH- - ]]

KKww = [H= [H33OO+ + ][OH][OH−− ] = 1.0 x 10] = 1.0 x 10−−1414

[OH[OH−− ] ] = = 1.0 x 10 1.0 x 10 -14-14 = 5 x 10= 5 x 10−−1212 M M 2 x 10 2 x 10 - 3- 3

SolutionSolution

3434

pH ScalepH Scale

The pH of a solutionThe pH of a solution

• is used to indicate the acidity of a solution. is used to indicate the acidity of a solution.

• has values that usually range from 0 to 14.has values that usually range from 0 to 14.

• is acidic when the values are less than 7.is acidic when the values are less than 7.

• is neutral with a pH of 7.is neutral with a pH of 7.

• is basic when the values are > 7.is basic when the values are > 7.

3535

pH of Everyday SubstancespH of Everyday Substances

3636

Testing the pH of SolutionsTesting the pH of Solutions

The pH of solutions can be determined using The pH of solutions can be determined using • a) pH metera) pH meter• b) pH paperb) pH paper• c) indicators that have specific colors at c) indicators that have specific colors at

different pH values.different pH values.

3737

pH is the negative log of the hydronium ion concentration.pH is the negative log of the hydronium ion concentration.

pH = - log [HpH = - log [H33OO++] ]

Example: Example: For a solution with [HFor a solution with [H33OO++] = 1 x 10] = 1 x 10−−4 4

pH =pH = −log [−log [1 x 101 x 10−−4 4 ]]

pH = - [-4.0]pH = - [-4.0]

pH = 4.0pH = 4.0

Note: The number of decimal places in the pH equalsNote: The number of decimal places in the pH equals

the significant figures in the coefficient of [Hthe significant figures in the coefficient of [H33OO++].].

4.4.00 1 SF in1 SF in 11 x 10x 10-4-4

Calculating pHCalculating pH

3838

[H[H33OO++], [OH], [OH--], and pH Values], and pH Values

3939

Calculating [HCalculating [H33OO++] from pH] from pH

The [HThe [H33OO++] can be expressed by using the pH as the ] can be expressed by using the pH as the negative power of 10.negative power of 10.

[H[H33OO++] = 1 x 10 ] = 1 x 10 --pH pH

For pH = 3.0, the [HFor pH = 3.0, the [H33OO++] = 1 x 10 ] = 1 x 10 --33

On a calculatorOn a calculator

1. Enter the pH value 1. Enter the pH value 3.0 3.0

2. Change sign 2. Change sign -3.0-3.0

3. Use the inverse log key (or 103. Use the inverse log key (or 10xx) to obtain) to obtain

the [Hthe [H3300++]. ]. = 1 x 10 = 1 x 10 --3 3 MM