Section 16.1
Properties of Acids and Bases
1. To understand two models of acids and bases
2. To understand how acids and bases ionize/dissociate in water
Learning Goals
Section 16.1
Properties of Acids and Bases
Acidic solutions have sour taste (tartness).
Ex.: citric acid in lemons, limes, oranges; acetic acid in vinegar
Basic (alkaline) solutions have bitter taste and are slippery.Ex.: soaps, “draino,” many
household cleaning products
Section 16.1
Properties of Acids and Bases
Acid, Base or Salt?
NaCl
NaOH
Ba(OH)2
HNO3
H2SO4
CaO
HCl
Mg(OH)2
NH3
LiOH
LiF
Section 16.1
Properties of Acids and Bases
Remember that… (add this to your notes)
Acid + Base Water + Salt
Ex.: HCl + NaOH H2O + NaCl
Acid-Base Reactions (review)
This is a double replacement reaction
Because H+ and OH- H2O
This is a neutralization reaction
Section 16.1
Properties of Acids and Bases Naming Acids (review)
If anion does NOT contain oxygen If anion contains oxygen
Prefix hydro-
Suffix –ic
attached to root name of element
suffix –ic if anion ends with –ate
suffix –ous if anion ends with –ite
attached to name of central element of anion / anion name
The following compounds dissolve in water to form acids:
HCl (hydrogen chloride) hydrochloric acid
HCN (hydrogen cyanide) hydrocyanic acid
H2S (dihydrogen sulfide) hydrosulfuric acid
Acid Anion Name
H2SO4 sulfate sulfuric acid
H3PO4 phosphate phosphoric acid
H2SO3 sulfite sulfurous acid
HNO2 nitrite nitrous acid
Section 16.1
Properties of Acids and Bases
A. Acids and Bases – Two Models
• Acid – produces hydrogen ions (H+) in aqueous solution
H2O
HCl(s) H+(aq) + Cl- (aq)
• Base – produces hydroxide ions (OH-) in aqueous solution H2O
NaOH(s) Na+(aq) + OH-(aq)
The Arrhenius Model (older) – Dissociation Reactions
Section 16.1
Properties of Acids and Bases
A. Acids and Bases – Two Models
• Acid – proton donor • Base – proton acceptor • The general reaction for an acid dissolving in water is
The Bronsted-Lowry Model (newer) – Dissociation & Reaction with Water
Section 16.1
Properties of Acids and Bases
A. Acids and Bases
The Bronsted-Lowry Model
• Water acts as a base accepting a proton from the acid.
• Forms hydronium ion (H3O+)
Section 16.1
Properties of Acids and Bases
A. Acids and Bases
The Bronsted-Lowry Model
• Water acts as an acid, donating a proton to the base. • Forms water molecule
NaOH + H2O Na+ + OH- + H2O
H+
Section 16.1
Properties of Acids and Bases
Ammonia is a base because it accepts a proton and becomes the ammonium ion:
NH3 + H+ NH4+
Ammonia ammonium, a polyatomic cation
Section 16.1
Properties of Acids and Bases
A. Acids and Bases
The Bronsted-Lowry Model
• Conjugate acid-base pairs
Section 16.1
Properties of Acids and Bases
The Bronsted-Lowry Model - Identifying Acid-Base Pairs
Do the two substances differ by a single proton?
HF, F- conjugate pair:HF H+ + F-
NH4+, NH3 conjugate pair:
NH4+ H+ + NH3
HCl, H2O not a conjugate pair:
Conj. base of HCl: Cl-
Conj. acid of H2O: H3O+
Section 16.1
Properties of Acids and Bases
The Bronsted-Lowry Model - Writing Conjugate Bases
The acid and its conjugate base must differ by a single proton.
Acid proton + conjugate base
1. HClO4 H+ + ClO4-
2. H3PO4 H+ + H2PO4-
3. CH3NH3+ H+ + CH3NH2
Section 16.1
Properties of Acids and Bases
Try to show the dissociation of each acid below into a proton and a conjugate base.
Acid proton + conjugate base
1. H2CO3 H+ + HCO3-
2. H3BO3 H+ + H2BO3-
3. H3PO3 H+ + H2PO3
-
4. HNO2 H+ + NO2-
Section 16.1
Properties of Acids and Bases
To understand the concept of acid strength
Learning Goals
Section 16.1
Properties of Acids and Bases
B. Acid Strength
• Strong acid – completely ionizes / dissociates• Forward reaction predominates
• Weak acid – most of the acid molecules remain intact
Section 16.1
Properties of Acids and Bases
B. Acid Strength
Section 16.1
Properties of Acids and Bases
B. Acid Strength
• A strong acid contains a relatively weak conjugate base.
• Water molecules compete with the base for the protons: a weak base loses (dissociation happens, strong acid), a strong base wins (little dissociation, weak acid)
Section 16.1
Properties of Acids and Bases
B. Acid Strength
• Common strong acids are
– Sulfuric acid, H2SO4
– Hydrochloric acid, HCl
– Nitric acid, HNO3
– Perchloric acid, HClO4
* Strong acids are strong electrolytes
good conductivity *
Section 16.1
Properties of Acids and Bases
B. Acid Strength / Acid Types
• Oxyacid – acidic proton is attached to an oxygen atom
– Typically a weak acid
• Organic acid – have a carbon atom backbone and commonly contain the carboxyl group
Section 16.1
Properties of Acids and Bases
Acid Strength / Acid Types
• Monoprotic acids can furnish only one proton.Ex.: HCl H+ + Cl-
• Diprotic acids can furnish two protons.Ex.: H2SO4 2H+ + SO4
2-
• Hydrohalic acids contain H attached to a halogen.Ex.: HCl (strong), HF (weak)
Section 16.1
Properties of Acids and Bases
B. Acid Strength
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