Acids and Bases. Properties of Acids/Bases Acids are substances which… Bases are substances which…
Chapter 20 Acids and Bases Describing Acids and Bases Hydrogen Ions and Acidity Acid-Base Theories...
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Transcript of Chapter 20 Acids and Bases Describing Acids and Bases Hydrogen Ions and Acidity Acid-Base Theories...
Chapter 20 Acids and Bases Describing Acids and Bases Hydrogen Ions and Acidity Acid-Base Theories Strengths of Acids and Bases
List as many properties of acids and bases as you can remember:
Properties of Acids
Properties of Bases
Determine if the following are acids or bases:
Lime
Vitamin C
DO NOT MIX
Ch 20.1 Describing Acids and Bases
Properties of Acids and Bases Names and Formulas of Acids and Bases
Properties of Acids Corrosive ('burns' your skin) Sour taste (e.g. lemons, vinegar) Contains hydrogen ions (H+) when
dissolved in water Has a pH less than 7 Turns blue litmus paper to a red color Reacts with bases to form salt and water Reacts with metals to form hydrogen gas Reacts with carbonates to form carbon
dioxide, water and a salt
Hydrofluoric Acid Burns
Properties of Bases Corrosive ('burns' your skin) Soapy feel Has a pH more than 7 Turns red litmus paper to a blue color Many alkalis (soluble bases) contain
hydroxyl ions (OH-) Reacts with acids to form salt and water
Sodium Hydroxide Burn
Names and Formulas of Acids
Anion Ending
Example Acid Name Example
-ide Cl- Hydro-(stem)-ic acid Hydrochloric Acid
-ite SO32- (stem) – ous acid Sulfurous Acid
-ate NO3- (stem) –ic acid Nitric Acid
Names and Formulas of Bases No Change Name the cation then the anion NaOH Sodium Hydroxide
Ch 20.2 Hydrogen Ions and Acidity Hydrogen Ions From Water The pH Concept Calculating pH Values Measuring pH
Hydrogen Ions From Water During the collisions of water molecules,
occasionally a hydrogen ion from one molecule is transferred to another
H2O + H2O H3O+ + HO-
This forms a hyrdronium ion and a hydroxide ion. Self Ionization
Hydrogen Ions Names:
Protons Hydrogen Ions Hydronium Ions Solvated Protons
H+ or H3O+
Neutral Solution The [ H+ ] equals [ OH- ]
Ion Product Constant for Water (Kw)
Kw = [ H+ ] [ OH- ] = 1.0x10-14 M2
Types of Solution Acidic Solution - [ H+ ] greater [ OH- ] Basic Solution - [ H+ ] less [ OH- ]
Alkaline Solutions
The pH Concept pH is a simpler way of writing [ H+ ]
pH = -log [ H+ ]
pH + pOH = 14
Arrhenius Acids and Bases 1887 Svante Arrhenius Acids – hydrogen containing compounds
that ionize to yield hydrogen ions in aqueous solutions
Bases - hydroxide containing compounds that ionize to yield hydroxide ions in aqueous solutions
Arrhenius Acids and Bases Monoprotic Acids – contain one ionizable
hydrogen HNO3
Diprotic Acids - contain two ionizable hydrogens H2SO4
Triprotic Acids - contain three ionizable hydrogens H3PO4
Arrhenius Acids and Bases Not all hydrogen's form ions Only those in very polar bonds
HCl CH4
Bronsted-Lowry Acids and Bases
1923 Johannes Bronsted and Thomas Lowry (independent of each other)
Acid – Hydrogen ion donor (proton donor) Base – Hydrogen ion acceptor (proton
acceptor)
Conjugate’s Conjugate Acid - Particle formed when a
base gains a hydrogen ion Conjugate Base - Particle formed when an
acid has donated a hydrogen ion HCl + H2O = H3O+ + Cl-
Acid Base Conjugate Acid Conjugate Base
Lewis Acids and Bases Gilbert Lewis (1875-1946) Lewis Acid – Substance that can accept a
pair of electrons to form a covalent bond Lewis Base - Substance that can donate a
pair of electrons to form a covalent bond
Strengths of Acids and Bases Strong and Weak Acids and Bases Calculating Dissociation Constants
Strong and Weak Acids and Bases
Strong Acid – completely ionized in aqueous solutions
Weak Acid – ionize only slightly in aqueous solutions
Acid Dissociation Constant Ka
The ratio of the concentration of the dissociated form of an acid to the concentration of the undissociated form
CH3COOH(aq) + H2O(l) = H3O+ (aq) + CH3COO-
(aq)
Ka = [H+] [CH3COO-]
[CH3COOH]
Acid Dissociation Constant Ka
Small Ka = weak acid 1.8 x 10-5
Large Ka = strong acid 4.4 x 10-4
Acid Dissociation Constant Ka
Diprotic and Triprotic acids lose their hydrogens one at a time, resulting in more than one Ka
H3PO4 7.5 x 10 –3
6.2 x 10 –8
4.8 x 10 –13
Bases Strong Base – dissociate completely into
metal ions and hydroxide ions in aqueous solutions
Weak Base – form the hydroxide ion and the conjugate acid of the base NH3(aq) + H2O(l) = NH4
+(aq) + OH-
(aq)
Kb = [NH4+] [OH-]
[NH3]
Base Dissociation Constant Kb
Kb = [conjugate acid] [OH-]
[conjugate base]
Small Kb = weak base
Large Kb = strong base