1 Announcements & Agenda (02/21/07) You should be reading Ch 8! Quiz on Friday: Ch 7 + Today Open 3pm Wed (Here!) Today 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 ( ) Acid & base strength: Quantitative ( ) Recommend: Do the Ch 8 CD tutorials!!! Recommend: Do the Ch 8 CD tutorials!!!

2 Last Time: Solubility & Temperature Depends on Temp!Depends on Temp! Solids: usually increases as temperature inc.Solids: usually increases as temperature inc. Gases: usually decreases as temperature inc.Gases: usually decreases as temperature inc.

3 Last Time: Solubility and Pressure Henry’s Law: Gas solubility is directly related to gas pressure above the liquidGas solubility is directly related to gas pressure above the liquid at higher pressures, more gas molecules dissolve in the liquid.at higher pressures, more gas molecules dissolve in the liquid. Real life examples… soda, the bends, etc.

4 The amount of solute dissolved in a specific amount of solution. amount of solute amount of solution Comes in all sorts of fantastic flavors! Mass Percent Mass Percent Volume Percent Volume Percent Mass/Volume Percent Mass/Volume Percent Molarity Molarity Last Time: Concentration

5 Last Time: Dilution 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 following equations:the concentrations and volumes are related by the following equations: For percent concentration: C 1 V 1 = C 2 V 2 initial diluted initial diluted For molarity: M 1 V 1 = M 2 V 2 initial diluted initial diluted

6 Last Time: Osmosis water (solvent) flows from the lower solute concentration into the higher solute concentration.water (solvent) flows from the lower solute concentration into the higher solute concentration. the level of the solution with the higher concentration rises.the level of the solution with the higher concentration rises. the concentrations of the 2 solutions become equal with time.the concentrations of the 2 solutions become equal with time.

7 Osmotic Pressure produced by the solute particles dissolved in a solution.produced by the solute particles dissolved in a solution. equal to the pressure that would prevent the flow of additional water into the more concentrated solution.equal to the pressure that would prevent the flow of additional water into the more concentrated solution. greater as the number of dissolved particles in the solution increases.greater as the number of dissolved particles in the solution increases.

8 Osmotic Pressure of the Blood Red blood cells have cell walls that are semipermeable membranes.have cell walls that are semipermeable membranes. maintain an osmotic pressure that cannot change or damage occurs.maintain an osmotic pressure that cannot change or damage occurs. must maintain an equal flow of water between the red blood cell and its surrounding environment.must maintain an equal flow of water between the red blood cell and its surrounding environment.

9 Isotonic Solutions exerts the same osmotic pressure as red blood cells.exerts the same osmotic pressure as red blood cells. is known as a “physiological solution”.is known as a “physiological solution”. of 5.0% glucose or 0.90% NaCl is used medically because each has a solute concentration equal to the osmotic pressure equal to red blood cells.of 5.0% glucose or 0.90% NaCl is used medically because each has a solute concentration equal to the osmotic pressure equal to red blood cells. H2O H2O

10 Hypotonic Solutions has a lower osmotic pressure than red blood cells.has a lower osmotic pressure than red blood cells. has a lower concentration than physiological solutions.has a lower concentration than physiological solutions. causes water to flow into red blood cells.causes water to flow into red blood cells. causes hemolysis: RBCs swell and may burst.causes hemolysis: RBCs swell and may burst. H2OH2O

11 Hypertonic Solutions has a higher osmotic pressure than RBCs.has a higher osmotic pressure than RBCs. has a higher concentration than physiological solutions.has a higher concentration than physiological solutions. causes water to flow out of RBCs.causes water to flow out of RBCs. cause crenation: RBCs shrinks in size.cause crenation: RBCs shrinks in size. H2OH2O

12 Dialysis In dialysis, solvent and small solute particles pass through an artificial membrane.solvent and small solute particles pass through an artificial membrane. large particles are retained inside.large particles are retained inside. waste particles such as urea from blood are removed using hemodialysis (artificial kidney).waste particles such as urea from blood are removed using hemodialysis (artificial kidney).

13 Chapter 8: Acids and Bases

14 25 Good Practice Problems (Ch 8) 8.01, 8.05, 8.07, 8.09, 8.11, 8.13, 8.15, 8.17, 8.19, 8.23, 8.25, 8.27, 8.33, 8.37, 8.41, 8.43, 8.45, 8.47, 8.49, 8.55, 8.61, 8.65, 8.67, 8.69, 8.71

15 Acids Arrhenius acids produce H + ions in water.produce H + ions in water. H 2 O H 2 O HCl(g) H + (aq) + Cl - (aq) are electrolytes.are electrolytes. have a sour taste.have a sour taste. May stingMay sting turn litmus (pH paper) red.turn litmus (pH paper) red. neutralize bases.neutralize bases.

16 Bases Arrhenius bases produce OH − ions in water.produce OH − ions in water. taste bitter or chalky.taste bitter or chalky. are electrolytes.are electrolytes. feel soapy and slippery.feel soapy and slippery. neutralize acids.neutralize acids.

17 Bronsted-Lowry Acids and Bases Another theory: the Br Ø nsted-Lowry theory… acids donate a proton (H + )acids donate a proton (H + ) bases accept a proton (H + )bases accept a proton (H + )

18 NH 3, a Br Ø nsted-Lowry Base In the reaction of ammonia and water, NH 3 is the base that accept H +.NH 3 is the base that accept H +. H 2 O is the acid that donates H +.H 2 O is the acid that donates H +.

19 A strong acid/base completely ionizes (100%) in aqueous solutions.A strong acid/base completely ionizes (100%) in aqueous solutions. HCl(g) + H 2 O(l) H 3 O + (aq) + Cl − (aq) COMPARE TO STRONG ELECTROLYTES A weak acid/base dissociates only slightly in water to form a few ions in aqueous solutions.A weak acid/base dissociates only slightly in water to form a few ions in aqueous solutions. H 2 CO 3 (aq) + H 2 O(l) H 3 O + (aq) + HCO 3 − (aq) H 2 CO 3 (aq) + H 2 O(l) H 3 O + (aq) + HCO 3 − (aq) COMPARE TO WEAK ELECTROLYTES Strengths of Acids/Bases: Ionization

20 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 formed after the proton is transferred).have weak conjugate bases (the product formed after the proton is transferred). Strong Acids (Know These)

21 Strong Bases are formed from metals of Groups 1A (1) and 2A (2).are formed from metals of Groups 1A (1) and 2A (2). include LiOH, NaOH, KOH, and Ca(OH) 2.include LiOH, NaOH, KOH, and Ca(OH) 2. dissociate completely in water.dissociate completely in water. KOH(s) K + (aq) + OH − (aq) KOH(s) K + (aq) + OH − (aq)

22 Weak Acids only a few molecules dissociate.only a few molecules dissociate. most of the weak acid remains as the undissociated (molecular) form of the acid.most of the weak acid remains as the undissociated (molecular) form of the acid. the concentrations of the H 3 O +the concentrations of the H 3 O + and the anion (A - ) are small. and the anion (A - ) are small. HA(aq) + H 2 O(l) H 3 O(aq) + A − (aq)

23 Weak Acids make up most of the acids.make up most of the acids. have relatively strong conjugate bases.have relatively strong conjugate bases.

24 NH 3 (g) + H 2 O(l) NH 4 + (aq) + OH − (aq) Weak Bases dissociate only slightly in water.dissociate only slightly in water. form only a few ions in water.form only a few ions in water.

25 In water occasionally, H + is transferred from 1 H 2 O molecule to another.H + is transferred from 1 H 2 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. H 2 O + H 2 O H 3 O + + OH − :O: H + H:O: H:O:H + + :O:H − :O: H + H:O: H:O:H + + :O:H − H H H H H H water water hydronium hydroxide ion (+) ion (-) water water hydronium hydroxide ion (+) ion (-) Ionization of Water: A Basis for Understanding pH (H+ concentrations)

26 Pure Water is Neutral (NOT ACIDIC OR BASIC) the ionization of water molecules produces small, but equal quantities of H 3 O + and OH − ions.the ionization of water molecules produces small, but equal quantities of H 3 O + and OH − ions. molar concentrations are indicated in brackets as [H 3 O + ] and [OH − ].molar concentrations are indicated in brackets as [H 3 O + ] and [OH − ]. [H 3 O + ] = 1.0 x 10 −7 M [H 3 O + ] = 1.0 x 10 −7 M [OH − ] = 1.0 x 10 −7 M [OH − ] = 1.0 x 10 −7 M

27 Acidic Solutions Adding an acid to pure water: increases the [H 3 O + ].increases the [H 3 O + ]. causes the [H 3 O + ] to exceed 1.0 x M.causes the [H 3 O + ] to exceed 1.0 x M. decreases the [OH − ].decreases the [OH − ].

28 Basic Solutions Adding a base to pure water: increases the [OH − ].increases the [OH − ]. causes the [OH − ] to exceed 1.0 x 10 − 7 M.causes the [OH − ] to exceed 1.0 x 10 − 7 M. decreases the [H 3 O + ].decreases the [H 3 O + ]. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

29 The ion product constant, K w, for water is the product of the concentrations of the hydronium and hydroxide ions.is the product of the concentrations of the hydronium and hydroxide ions. K w = [ H 3 O + ] [ OH − ] can be obtained from the concentrations in pure water.can be obtained from the concentrations in pure water. K w = [ H 3 O + ] [ OH − ] K w = [1.0 x 10 − 7 M] x [ 1.0 x 10 − 7 M] = 1.0 x 10 − 14 = 1.0 x 10 − 14 Ion Product of Water, K w

30 [H 3 O + ] and [OH − ] in Solutions IMPORTANT: K w is always 1.0 x 10 −14.

31 Calculating [H 3 O + ] What is the [H 3 O + ] of a solution if [OH − ] is 5.0 x M? STEP 1: Write the K w for water. K w = [H 3 O + ][OH − ] = 1.0 x 10 −14 STEP 2: Rearrange the K w expression. [H 3 O + ] = 1.0 x [OH − ] [OH − ] STEP 3: Substitute [OH − ]. [H 3 O + ] = 1.0 x = 2.0 x M [H 3 O + ] = 1.0 x = 2.0 x M 5.0 x x

32 If lemon juice has [H 3 O + ] of 2 x 10 −3 M, what is the [OH − ] of the solution? 1) 2 x 10 −11 M 2) 5 x 10 −11 M 3) 5 x 10 −12 M

33 3) 5 x 10 −12 M Rearrange the K w to solve for [OH - ] K w = [H 3 O + ][OH − ] = 1.0 x 10 −14 [OH − ] = 1.0 x = 5 x 10 −12 M 2 x x Solution

34 pH Scale The 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.

35 pH of Everyday Substances

36 Testing the pH of Solutions 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 different pH values.c) indicators that have specific colors at different pH values.

37 pH is the negative log of the hydronium ion concentration. pH = - log [H 3 O + ] Example: For a solution with [H 3 O + ] = 1 x 10 −4 pH =−log [1 x 10 −4 ] pH = - [-4.0] pH = 4.0 Note: The number of decimal places in the pH equals the significant figures in the coefficient of [H 3 O + ]. the significant figures in the coefficient of [H 3 O + ] SF in 1 x Calculating pH

38 [H 3 O + ], [OH - ], and pH Values

39 Calculating [H 3 O + ] from pH The [H 3 O + ] can be expressed by using the pH as the negative power of 10. [H 3 O + ] = 1 x 10 -pH For pH = 3.0, the [H 3 O + ] = 1 x On a calculator 1. Enter the pH value Change sign Use the inverse log key (or 10 x ) to obtain the [H ]. = 1 x M the [H ]. = 1 x M