CHM 103 Lecture 16a S07

Announcements & Agenda (02/21/07): 

Announcements & Agenda (02/21/07) You should be reading Ch 8! Quiz on Friday: Ch 7 + Today Open Review/Problems @ 3pm Wed (Here!) Today Osmosis (7.7) What are acids & bases? (8.1, 8.2) Acid & base strength: Qualitative (8.3) Acid & base strength: Quantitative (8.4-8.5) Recommend: Do the Ch 8 CD tutorials!!!

Last Time: Solubility & Temperature: 

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

Last Time: Solubility and Pressure: 

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

Last Time: Concentration: 

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 Volume Percent Mass/Volume Percent Molarity Last Time: Concentration

Last Time: Dilution: 

Last Time: Dilution In the initial and diluted solution, the amount of solute is the same. the concentrations and volumes are related by the following equations: For percent concentration: C1V1 = C2V2 initial diluted For molarity: M1V1 = M2V2 initial diluted

Last Time: Osmosis: 

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

Osmotic Pressure: 

Osmotic Pressure 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. greater as the number of dissolved particles in the solution increases.

Osmotic Pressure of the Blood: 

Osmotic Pressure of the Blood Red blood cells have cell walls that are semipermeable membranes. 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.

Isotonic Solutions: 

Isotonic Solutions exerts the same osmotic pressure as red blood cells. 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. H2O

Hypotonic Solutions: 

Hypotonic Solutions has a lower osmotic pressure than red blood cells. has a lower concentration than physiological solutions. causes water to flow into red blood cells. causes hemolysis: RBCs swell and may burst. H2O

Hypertonic Solutions: 

Hypertonic Solutions has a higher osmotic pressure than RBCs. has a higher concentration than physiological solutions. causes water to flow out of RBCs. cause crenation: RBCs shrinks in size. H2O

Dialysis: 

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

Chapter 8: Acids and Bases: 

Chapter 8: Acids and Bases

25 Good Practice Problems (Ch 8): 

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

Acids: 

Acids Arrhenius acids produce H+ ions in water. H2O HCl(g) H+(aq) + Cl- (aq) are electrolytes. have a sour taste. May sting turn litmus (pH paper) red. neutralize bases.

Bases: 

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

Bronsted-Lowry Acids and Bases: 

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

NH3, a BrØnsted-Lowry Base: 

NH3, a BrØnsted-Lowry Base In the reaction of ammonia and water, NH3 is the base that accept H+. H2O is the acid that donates H+.

Strengths of Acids/Bases: Ionization: 

A strong acid/base completely ionizes (100%) in aqueous solutions. HCl(g) + H2O(l) H3O+ (aq) + Cl− (aq) COMPARE TO STRONG ELECTROLYTES A weak acid/base dissociates only slightly in water to form a few ions in aqueous solutions. H2CO3(aq) + H2O(l) H3O+(aq) + HCO3− (aq) COMPARE TO WEAK ELECTROLYTES Strengths of Acids/Bases: Ionization

Strong Acids (Know These): 

make up six (just a few) of all the acids. have weak conjugate bases (the product formed after the proton is transferred). Strong Acids (Know These)

Strong Bases: 

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

Weak Acids: 

Weak Acids only a few molecules dissociate. most of the weak acid remains as the undissociated (molecular) form of the acid. the concentrations of the H3O+ and the anion (A-) are small. HA(aq) + H2O(l) H3O(aq) + A−(aq)

Weak Acids: 

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

Weak Bases: 

NH3(g) + H2O(l) NH4+(aq) + OH−(aq) Weak Bases dissociate only slightly in water. form only a few ions in water.

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

In water occasionally, H+ is transferred from 1 H2O molecule to another. one water acts an acid, the another acts as a base. H2O + H2O H3O+ + OH− .. .. .. .. :O: H + H:O: H:O:H + + :O:H− .. .. .. .. H H H water water hydronium hydroxide ion (+) ion (-) Ionization of Water: A Basis for Understanding pH (H+ concentrations)

Pure Water is Neutral (NOT ACIDIC OR BASIC): 

Pure Water is Neutral (NOT ACIDIC OR BASIC) the ionization of water molecules produces small, but equal quantities of H3O+ and OH− ions. molar concentrations are indicated in brackets as [H3O+] and [OH−]. [H3O+] = 1.0 x 10−7 M [OH−] = 1.0 x 10−7 M

Acidic Solutions: 

Acidic Solutions Adding an acid to pure water: increases the [H3O+]. causes the [H3O+] to exceed 1.0 x 10-7 M. decreases the [OH−].

Basic Solutions: 

Basic Solutions Adding a base to pure water: increases the [OH−]. causes the [OH−] to exceed 1.0 x 10− 7M. decreases the [H3O+]. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

Ion Product of Water, Kw: 

The ion product constant, Kw, for water is the product of the concentrations of the hydronium and hydroxide ions. Kw = [ H3O+] [ OH− ] can be obtained from the concentrations in pure water. Kw = [ H3O+] [ OH− ] Kw = [1.0 x 10− 7 M] x [ 1.0 x 10− 7 M] = 1.0 x 10− 14 Ion Product of Water, Kw

[H3O+] and [OH−] in Solutions: 

[H3O+] and [OH−] in Solutions IMPORTANT: Kw is always 1.0 x 10−14.

Calculating [H3O+]: 

Calculating [H3O+] What is the [H3O+] of a solution if [OH−] is 5.0 x 10-8 M? STEP 1: Write the Kw for water. Kw = [H3O+ ][OH− ] = 1.0 x 10−14 STEP 2: Rearrange the Kw expression. [H3O+] = 1.0 x 10-14 [OH−] STEP 3: Substitute [OH−]. [H3O+] = 1.0 x 10-14 = 2.0 x 10-7 M 5.0 x 10- 8

If lemon juice has [H3O+] of 2 x 10−3 M, what is the [OH−] of the solution?: 

If lemon juice has [H3O+] 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

Solution: 

3) 5 x 10−12 M Rearrange the Kw to solve for [OH- ] Kw = [H3O+ ][OH− ] = 1.0 x 10−14 [OH− ] = 1.0 x 10 -14 = 5 x 10−12 M 2 x 10 - 3 Solution

pH Scale: 

pH Scale The pH of a solution is used to indicate the acidity of a solution. has values that usually range from 0 to 14. is acidic when the values are less than 7. is neutral with a pH of 7. is basic when the values are > 7.

pH of Everyday Substances: 

pH of Everyday Substances

Testing the pH of Solutions: 

Testing the pH of Solutions The pH of solutions can be determined using a) pH meter b) pH paper c) indicators that have specific colors at different pH values.

Calculating pH: 

pH is the negative log of the hydronium ion concentration. pH = - log [H3O+] Example: For a solution with [H3O+] = 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 [H3O+]. 4.0 1 SF in 1 x 10-4 Calculating pH

[H3O+], [OH-], and pH Values: 

[H3O+], [OH-], and pH Values

Calculating [H3O+] from pH: 

Calculating [H3O+] from pH The [H3O+] can be expressed by using the pH as the negative power of 10. [H3O+] = 1 x 10 -pH For pH = 3.0, the [H3O+] = 1 x 10 -3 On a calculator 1. Enter the pH value 3.0 2. Change sign -3.0 3. Use the inverse log key (or 10x) to obtain the [H30+]. = 1 x 10 -3 M