Acids & Bases
Properties
Acid-Base Theories
Acid-Base Reactions
Properties
Both conduct electricity (electrolytes) because they
break apart to some degree in water.
Acids produce H+ (proton) in water.
Bases produce OH- (hydroxide) in water.
Samples:
Acids: vinegar(acetic acid), lactic acid in sour
milk, citric acid,
Bases: ammonia, lye (NaOH), Milk of Magnesia
Mg(OH)2.
More on Acids
1. Sour taste. NEVER taste acids in lab
situations.
2. Change color of indicators.
3. Some acids react with metals & release H2
gas.
4. Acids react with bases to produce salt &
water. When neutralization occurs, #1.-#3
disappear.
5. Conduct electric current.
Neutralization Reaction
Acid + Base --> Salt + Water
HCl + NaOH --> NaCl + H20
H2SO4 + Ca(OH)2 --> CaSO4 + 2H20
Acid Nomenclature
• Binary Acids contain Hydrogen and another
element:
• Hydro + root of 2nd element + ic
– HF
– HCl
– HBr
– HI
– H2S
hydrofluoric acid
hydrochloric acid
hdrobromic acid
hydroiodic …
hydrosulfuric …
Oxyacids
• Contain H, O, and a 3rd element. More are
listed in your book.
Common Industrial Acids
•
•
•
•
•
Sulfuric
Nitric
Phosphoric
Hydrochloric
Acetic
Bases
• Bitter taste (NEVER taste bases in labs).
• Change the color of indicators.
• Slippery feel (dilute bases, don’t touch
concentrated bases)
• React with acids to produce salt & water
• Conduct electric current.
Arrhenius Acids & Bases
• Arrhenius Acid is a chemical compound that
increases the concentration of hydrogen
ions, H+, in aqueous solutions.
• Arrhenius Base is a chemical compound that
increases the concentration of hydroxide ions,
OH-, in aqueous solutions.
• When put with water, these compounds
dissociate (break apart) forming ions
• HNO3 (l) + H20 (l) --> NO3- (aq) + H30+ (aq)
• When put in water, HNO3 , ionizes and the
charged particles formed can conduct
electricity.
• The amount of H30+ (hydronium) produced is
an indication of the acid’s strength.
Strong Acids ionize
completely in water.
Weak Acide release few
hydrogen ions in water.
Strong Acids:
• HI
• HClO4
• HBr
• HCl
• H2SO4
• HClO3
Weak Acids:
• HSO4• H3PO4
• HF
• CH3COOH
• H2CO3
• H2S
• HCN
• HCO3-
For Bases, the strength depends on
how it dissociates (ionizes)
Strong Bases ionize completely.
Strong Bases
• Ca(OH)2 --> Ca2+ + 2OH• Sr(OH)2
• Ba(OH)2
• NaOH
• KOH
• RbOH
• CsOH
Weal Bases ionize slightly.
Weak Bases
• NH3 + H2O
NH4+ + OH• C6H5NH2
“
“
means the reaction is
reversible
Assignment
• #72: 476/1-4
• #75: 491/1,4-11
Acid-Base Theories
Bronsted-Lowry Acids donate protons (H+)
Molecules or ions can donate protons.
HCl + NH3  NH4+ + Cl-
The HCl is a Bronsted-Lowry Acid. It donates a proton to water
Water can act as a Bronsted-Lowry Acid also as in the following reaction:
H2O (l) + NH3
OH- + NH4+
Bronsted-Lowry Bases
accept protons. In the equation below, ammonia
is the base, because it accepts the proton to
become an ammonium ion.
acid base
HCl + NH3  NH4 +
+
Cl
Mono- and Polyprotic Acids
• Monoprotic acids can only donate one proton
per molecule. Ex.: HCl, HNO3
• Polyprotic acids can donate 2 or more protons
per molecule. Ex.: H2SO4, H3PO4
• For polyprotic acids the donations occur in
stages, losing one H+ at a time.
Lewis Acids and Bases
• Arrhenius and Bronsted-Lowery definitions
have some limitations. Lewis classification is
based on bonding and structure including
substances without hydrogen. The Lewis
classification is more complete than the other
2 methods.
A Lewis acid
is an atom, ion or molecule that accepts an
electron pair to form a covalent bond.
Dot notation
Structural formula
– a bar represents
what?
A pair of shared
electrons.
A Lewis base
is an atom, ion, or molecule that donates an
electron pair to form a covalent.
Lewis Acid-Base Reaction
• is the formation of one or more covalent
bonds between an electron-pair donor and an
electron-pair acceptor.
Pair of
donated
electrons
Assignment:
• #73: 482/1,2
• #76: 491/12-15,17,18
• Samples are done on the next 2 frames.
491/15. Dilute HCl(aq) and KOH(aq) are mixed in
chemically equivalent quantities.
a) Write the formula equation for the reaction.
HCl(aq) + KOH(aq) --> KCl(aq) + H2O(l)
b) Write the overall ionic equation.
H3O+(aq) + Cl-(aq) + K+(aq) + OH-(aq) -->
K+(aq) + Cl-(aq) + 2H20(l)
c) Write the net ionic equation.
H3O+(aq) + OH-(aq) --> 2H20(l)
492/17a. Write the formula equation and
net ionic equation for this reaction.
Formula equation for: Zn(s) + HCl(aq) -->
Zn(s) + 2HCl(aq) --> ZnCl2(aq) + H2(g)
Overall ionic equation:
Zn(s) + 2H3O+(aq) + 2Cl-(aq) -->
Zn2+(aq) + 2Cl-(aq) + H2(g) + 2H20(l)
Net ionic equation:
Zn(s) + 2H30+(aq) --> Zn2+(aq) + H2(g) + 2H20(l)
Acid-Base Reactions
• Now we are going to use Bronsted-Lowry
description to explore acid-base reactions.
• What was the Bronsted-Lowery theory?
• B-L acid donates protons
• B-L base accepts protons
• A conjugate base is the species that remains
after a Bronsted-Lowery acid has given up a
proton.
• A conjugate acid is the species that forms
when a Bronsted-Lowery base gains a proton.
Acid-Base Reactions
Now we are going to use Bronsted-Lowry
definitions to study Acid-Base reactions.
The species that remains after a Bronsted-Lowry
acid has given up a proton is the conjugate
base of that acid.
HF
+ H2O
F+
H30+
Acid
conjugate
base
The species that is formed when a BronstedLowry base gains a proton is the conjugate
acid of that base.
HF(aq) + H2O(l)
F-(aq) + H30+(aq)
Base
conjugate
acid
HF(aq) + H2O(l)
Acid
Base
acid1
base2
Conjugate pairs:
(1) HF and F(2) H20 and H30+
F-(aq) +
conjugate
base
base1
H30+(aq)
conjugate
acid
acid2
Strength of Conjugate Acids & Bases
• On Page 1 of your handout for this chapter,
you have a table which lists and compares the
strengths of various acids and their conjugate
bases. Get your Ch. 14 handout out now.
Determining direction of equilibrium in
Acid-Base reactions
The stronger an acid is, the weaker its conjugate
base will be.
The stronger a base is, the weaker its conjugate
acid will be.
From these concepts, we can predict the
outcome of a reaction.
Assignment for this section:
#74: 489/1,2
#77: 491/19-25
#78: 492/26-30,36,37 (Overall practice problems)
Sample problem on next page:
492/23a: Identify the proton donor or acid and
the proton acceptor or base. Label each acidbase conjugate pair.
CH3COOH + H20
H30+ + CH3COOacid
base
conjugate conjugate
acid
base
Another sample.
492/29a. Write the formula equation, the
overall ionic equation, and the net ionic
equation for a neutralization reaction that
would form RbClO4.
Formula equation:
RbOH(aq) + HClO4(aq) --> RbClO4(aq) + H20(l)
Overall Ionic equation:
Rb+(aq) + OH-(aq) + H30+(aq) + ClO4-(aq) -->
Rb+(aq) + ClO4-(aq) + 2H20(l)
Net ionic equation:
H30+(aq) + OH-(aq) --> 2H20(l)
Amphoteric Compounds
These can act as either an acid or a base.
Water acts as a base in this reaction:
H2SO4(aq) + H20(l) --> H30+(aq) + HSO4-(aq)
acid1
base2
acid2
base1
But, water acts as an acid here:
NH3(g) + H20(l)
NH4+(aq) + OH-(aq)
Base1
acid2
acid1
base2
Review
Acids
Bases
Arrhenius
concentration of:
[H+]
[OH-]
Bronsted-Lowry
H+ donor H+ acceptor
Lewis, electron pair: acceptor donor