10.1 & 10.2
ACIDS AND BASES
PROPERTIES OF ACIDS
AND BASES
Acids
pH
Electrical
conductivity
Taste
Feel
Colour with
litmus paper
Colour with
phenolphthalein
Bases
PROPERTIES OF ACIDS
AND BASES
Acids
pH
Electrical
conductivity
Taste
Feel
Colour with
litmus paper
Colour with
phenolphthalein
less than 7
Bases
greater than 7
PROPERTIES OF ACIDS
AND BASES
Acids
pH
Electrical
conductivity
Taste
Feel
Colour with
litmus paper
Colour with
phenolphthalein
less than 7
Bases
greater than 7
conductivity varies
PROPERTIES OF ACIDS
AND BASES
Acids
pH
less than 7
Electrical
conductivity
Taste
Feel
Colour with
litmus paper
Colour with
phenolphthalein
Bases
greater than 7
conductivity varies
sour
bitter
PROPERTIES OF ACIDS
AND BASES
Acids
pH
less than 7
Electrical
conductivity
Bases
greater than 7
conductivity varies
Taste
sour
bitter
Feel
no special feel
slippery
Colour with
litmus paper
Colour with
phenolphthalein
PROPERTIES OF ACIDS
AND BASES
Acids
pH
less than 7
Electrical
conductivity
Bases
greater than 7
conductivity varies
Taste
sour
bitter
Feel
no special feel
slippery
Colour with
red
litmus paper
Colour with
phenolphthalein
blue
PROPERTIES OF ACIDS
AND BASES
Acids
pH
less than 7
Electrical
conductivity
Bases
greater than 7
conductivity varies
Taste
sour
bitter
Feel
no special feel
slippery
Colour with
red
litmus paper
Colour with
colourless
phenolphthalein
blue
pink
REACTIONS OF ACIDS
Acids react with metals to produce hydrogen gas
Magnesium + hydrochloric acid  magnesium chloride + hydrogen
gas
Hydrochloric acid also reacts with carbonate compounds to
produce carbon dioxide
REACTIONS OF BASES
Bases react with carbon dioxide to form carbonates
Calcium hydroxide + carbon dioxide  calcium carbonate + water
NAMING ACIDS
Binary Acids
•composed of two elements: hydrogen and a non-metal ex. HF (aq)
•typically a hydrogen attached to a halogen and dissociated in water,
hence the “aq”
HF  F- + H+
•begin with the prefixes “hydro”
HCl (aq) = hydrochloric acid
HBr (aq) =
Oxoacids
•formed from a polyatomic ion that contains oxygen, hydrogen and
another element. They have NO overall charge
Hypo --- ous
Hyponitrous acid
HNO
--- ous
Nitrous acid
HNO2
HClO
HClO2
H2CO
H2CO2
H2SO2
H2SO3
H3PO2
H3PO3
--- ic
Per --- ic
Nitric acid
Pernitric acid
HNO3
HNO4
Chloric acid
HClO3
HClO4
Carbonic acid
H2CO3
H2CO4
Sulfuric acid
H2SO4
H2SO5
Phosphoric acid
H3PO4
H3PO5
NAMING BASES
Ionic hydroxides
NaOH =
Hydroxide bases only show their basic properties when
they are in solution; thus, we use (aq) in the formula of a
base.
ARRHENIUS THEORY OF ACIDS AND BASES
• An acid is a substance that ionizes in water to produce one or more
hydrogen ions, H+
• Example:
H2SO4 (aq)  2 H+ (aq) + SO4 2- (aq)
• A base is a substance that dissociates in water to produce one
or more hydroxide ions, OH• Example: Ca(OH)2 (aq) 
Ca 2+ (aq) + 2 OH- (aq)
• Ionization vs dissociation
• Both occur when a compound breaks apart in water, causing the
presence of ions
• Dissociation occurs when water molecules pull the + and – ions apart
• Ionization involves the formation of ions from uncharged molecules,
causing uncharged entities to become ionized. How? Arrhenius didn’t
say!
• In water, ionic compounds DISSOCIATE and molecular compounds
IONIZE.
• Thankfully, the chemical equations look the same!
BRøNSTED LOWRY THEORY OF
ACIDS AND BASES
A broader definition of acids and bases
BRØNSTED ACID: Substance that donates an H+ (proton)
BRØNSTED BASE: Substance that accepts an H+ (proton)
Under this definition, a substance can ONLY act as an acid
(donating a proton) IF another substance is acting as a
base at the same time.
BRøNSTED LOWRY THEORY OF
ACIDS AND BASES
Two molecules or ions that are related by the transfer of a
proton are called: A CONJUGATE ACID-BASE PAIR
EVERY BRØNSTED ACID has a conjugate base that forms after
the acid has donated its H+ (proton).
EVERY BRØNSTED BASE has a conjugate acid that forms after the
base has accepted a H+ (proton).
HNO3 + N2H4  NO3ACID
BASE
+
N2H5+
CONJUGATE CONJUGATE
BASE
ACID
H2PO4 + CO32-  HPO42- + HCO3ACID
S2-
BASE
BASE
CONJUGATE CONJUGATE
BASE
ACID
+ H2O  HSACID
+
OH-
CONJUGATE CONJUGATE
ACID
BASE
COMPARING ACIDS
Strong Acids
Weak Acids
COMPARING ACIDS
Strong Acids
Weak Acids
Completely ionize in water
Partially ionize in water
COMPARING ACIDS
Strong Acids
Weak Acids
Completely ionize in water
Partially ionize in water
React very quickly
React mildly
COMPARING ACIDS
Strong Acids
Weak Acids
Completely ionize in water
Partially ionize in water
React very quickly
React mildly
Low pH (0-4)
Moderate pH (4-7)
COMPARING ACIDS
Strong Acids
Weak Acids
Completely ionize in water
Partially ionize in water
React very quickly
React mildly
Low pH (0-4)
Moderate pH (4-7)
Good conductors
Poor conductors
COMPARING ACIDS
Strong Acids
Weak Acids
Completely ionize in water
Partially ionize in water
React very quickly
React mildly
Low pH (0-4)
Moderate pH (4-7)
Good conductors
Poor conductors
Examples
HCl (stomach acid)
HNO3 (used in rocket fuel)
H2SO4 (in car batteries)
Examples
CH3COOH (vinegar)
H3PO4 (in pop)
COMPARING BASES
Strong Bases
Weak Bases
Completely ionize in water
Partially ionize in water
React very quickly
React mildly
High pH (11-14)
Moderate pH (7-11)
Good conductors
Poor conductors
Examples
NaOH (in oven/drain cleaner)
Ca(OH)2 (limewater)
Examples
NH3 (Ammonia)
**STRENGTH and CONCENTRATION of
acids/bases are not related!
• Diluting A STRONG ACID does not make it a
weak acid.
• ie: HCl is always a strong acid, regardless of
whether its [ ] is 20 mol/L or 0.001 mol/L
• It will always completely ionize in water,
regardless of concentration!!
• Similarly, a WEAK ACID can be very
concentrated.
STRONG AND WEAK ACIDS
Acidic solutions that have high electrical conductivity are
considered STRONG ACIDS
In these solutions almost all (>99%) the acid ionizes
(produces ions)
Typically these acids are highly corrosive HCl, HNO3, H2SO4
WEAK ACIDS have low percentage ionization, i.e. they only
ionize partially (<50%)
Examples of weak acids are H2CO3 and HCH3COO
STRONG AND WEAK BASES
An ionic hydroxide compound that dissociates
completely (>99%) in solution is considered a
STRONG BASE
Similar to acids, weak bases do not dissociate
completely
Some weak bases do not contain a hydroxide ion
but, when dissolved in solution, produce hydroxide
ions
Example: ammonia
NH3 + H2O  NH4+ + OH-
MONOPROTIC ACIDS
Contain a single hydrogen ion that can dissociate (can only
lose one proton).
Example: HCl(aq) 
H+(aq) +
Cl-(aq)
What are diprotic acids and triprotic acids?
EXAMPLE OF A TRIPROTIC ACID
H3PO4(aq) + H2O(l) ↔
H+(aq) + H2PO4-(aq)
H2PO4-(aq) + H2O(l) ↔
H+(aq) + HPO42-(aq)
HPO4(aq) + H2O(l)
↔
H+(aq) + PO4-(aq)
*FIRST DISSOCIATION IS STRONGER THAN SECOND DISSOCIATION.
pH
In pure water, (neutral solution), a very low
concentration of water molecules ionize to
produce hydronium ions and hydroxide ions
•
S.P. Sorenson proposed that the acidity of a
solution be expressed in terms of a quantity
known as pH
The pH of solution is related to the quantity of
hydronium ions (H3O+) in a given amount of
solution, in the mathematical expression
pH
• pH = “power of hydrogen”
• pH scale is measurements by powers of ten
• pH of 3 is 10 times more acidic than pH of 4
100 times more __________than
basic
• pH of 10 is _______
pH of 8
• Indicators are substances that will change different colours in the presence
of an acid or base
ACID BASE INDICATORS
Indicators can be used to determine the
whether a solution is acidic or basic
We must choose the right indicator!
pH of a Solution
Recall…
•
Acids release H+ when they ionize in water
•
Concentration is the amount of a solute in a
given volume of solvent
These two concepts have been combined to describe
the acidity of a solution (or pH)
•
pH is the concentration of H3O+ (or H+) in a
solution
pH of a Solution
Also recall (according to Arrhenius)…
Acidic solutions have a higher concentration of
hydronium ions
Basic solutions have a higher concentration of
hydroxide ions
Thus, the pH scale works by determining the
hydronium ion concentration
pH Scale
Pure water has a hydronium concentration of
1 x 10-7 mol/L
Thus,
In an acidic solution: [H3O+] > 1 x 10-7 mol/L
In a basic solution: [H3O+] < 1 x 10-7 mol/L
pH Scale
From this:
The pH of a solution is defined as the negative
of the exponent to the base 10 of the hydrogen
ion concentration
+
[H ]
=
-pH
10
pH Scale
Example: What is the [H+] of a solution with a pH
of 3?
[H+] = 10-pH
[H+] = 10-3
[H+] = 1.0 x 10-3 mol/L
pH Scale
Example: What is the [H+] of a solution with a pH
of 10.33?
[H+] = 10-pH
[H+] = 10-10.33
[H+] = 4.7 x 10-11 mol/L
pH Scale
To determine the pH of a solution, the following
equation would need to be used:
pH = -log[H+]
Example: What is the pH of an antacid solution with
a hydrogen ion concentration of 5.3 x 10-11?
pOH
The same formulas can be used to find the concentration of base
pOH = -log[OH-]
[OH-] = 10-pOH
pH + pOH = 14
• PG 469 # 1, 2, 4, - 8, 9, 10
• PG 475 # 1,4-11