Reactions Between Ions
in Aqueous
Aq eo s Sol
Solutions
tions
Ionic Equations
Electrolyte is a substance that
conducts electricity when it is
melted or dissolved in water;
aqueous solutions of
electrolytes contain ions.
1
Acid is a substance that increases
the concentration of H+ (or H3O+)
ions when it is dissolved in water.
Examples: HC2H3O2; HCl
Base is a substance that increases
the concentration of OH- ions when
it is dissolved in water.
Examples: KOH; NH3
2
Acetic Acid
(active ingredient of vinegar)
CH3COOH
or
HC2H3O2
Acetic Acid
Dissolved in
Water
ate (Vinegar
ega )
3
Acid is a substance that increases
the concentration of H+ ions when it
is dissolved in water.
Examples: acetic acid (HC2H3O2, a weak
acid); hydrochloric acid (HCl, a strong
acid)
4
molecule
(g)
Strong Acids are
Completely Ionized
in Aqueous Solutions
ions
Strong and Weak Acids
5
Seven Common Strong Acids*
H2SO4 (aq)
sulfuric acid (strong acid only in its
HNO3 (aq)
nitric acid
HClO4 (aq)
perchloric acid
HClO3 (aq)
chloric acid
HCl(aq)
hydrochloric acid
HBr(aq)
hydrobromic acid
HI(aq)
hydroiodic acid
first ionization step)
*
Almost all acids that are not on this list are weak acids. In an aqueous solution
only about 1% of the molecules of a weak acid splits into ions.
6
Seven Common Strong Acids
Two WellKnown Acids
Three Group 7A
Nonoxy Acids
Two Chlorine
Oxyacids
nitric, HNO3
hydrochloric, HCl chloric, HClO3
sulfuric, H2SO4
hydrobromic,
y
HBr p
perchloric, HClO3
hydroiodic, HI
Memorize
third!!!
Memorize
first!!!
Memorize
second!!!
7
8
Phosphoric Acid
H3PO4
Sulfuric Acid
H2SO4
Carbonic Acid
H2CO3
Nitric Acid
HNO3
9
Sulfuric Acid
H2SO4
Sulfate Ion
SO42−
H2SO4
molecule
10
Ba2+
SO42-
Barium Sulfate
Carbonic Acid
H2CO3
Carbonate Ion
2−
2− CO3
2
11
An Ionic Compound with
Polyatomic Ions (CaCO3)
Ca2+
CO 32-
Arrangement of Ions in Solid Ammonium Chloride, NH4Cl(s)
−
12
Nitric Acid
HNO3
one O less
Nitrous Acid
HNO2
13
Base is a substance that increases
the concentration of OH- ions when
it is dissolved in water.
Examples: KOH; NH3
NH3(g) Ammonia Gas
NH3(aq) Aqueous Solution of Ammonia
or
“Ammonium Hydroxide”
14
NH3 is ammonia (molecule; compound, substance)
NH4+ is ammonium ion
(polyatomic ion; not a compound per se,
b t can be
but
b a partt off ionic
i i compound)
d)
No lone pairs
Tetrahedral
shape
15
Reactions in Aqueous
S l ti
Solutions
= all or at least some of the
reactants and products are
dissolved in water
16
Water in Chemical Reactions
• Water can be just a reaction medium: in a
chemical equation its presence is indicated
by (aq) for substances that are soluble in
water and no H2O is written on either side
of the equation.
• Water can be a reactant: H2O(l) is written
on the
h left
l f side
id off the
h equation.
i
• Water can be a product: H2O(l) is written
on the right side of the equation.
Ionic Equations
17
Types of Chemical Equations
• Complete
p
Formula Equation
q
(“molecular” equation)
• Complete Ionic Equation (CIE)
• Net
N t iionic
i Equation
E
ti
(NIE)
Ionic equations are chemical
equations which are written only for
reactions in aqueous solutions. In ionic
equations substances are written in
their predominant forms (as atoms or
molecules or as ions).
Charges must be shown for ions!!!
18
Split or Not to Split?
In ionic equations, split into ions
and write the ions with “+”
+ and “-”
- :
• Seven strong acids
H2SO4
HNO3
HClO4
HCl
HBr
HI
HClO3
• All soluble ionic compounds
Examples: NH4Cl
KOH
Cu(NO3)2
Never split into ions anything else!!!
Double Displacement Reactions
“Driving force”: removing ions in one of
the following three ways.
• One of the products is insoluble
– Precipitation Reactions
• Water (or another weak electrolyte)
is formed
– Acid-Base Reactions (if water is the product)
• One of the products is gas
– Gas-Evolution Reactions
19
Precipitation Reactions
SOLUBILITY RULES FOR IONIC COMPOUNDS
Do not use this table to determine the solubility of covalent compounds! Acids are covalent
compounds. Most inorganic acids and many organic acids are highly soluble in water.
Soluble*
Exceptions
Insoluble
*
Slightly Soluble
Sodium, potassium, and
ammonium salts
None
None
Nitrates
None
None
Chlorates
None
None
Perchlorates
None
K+
+
Ag , Hg22+
Acetates
None
Fluorides
Mg2+, Ca2+, Sr2+, Ba2+, Pb2+,
Cu2+, Al3+, Sn2+
Chlorides, bromides and
iodides
Ag+, Hg22+, Hg2+, PbI2 , Cu+
Sulfates
**
2+
2+
2+
Sr , Ba , Pb
Insoluble
Carbonates
Phosphates
Sulfides
Hydroxides
*
None
**
**
PbCl2 , PbBr2
2+
+
Ca , Ag ,
Hg22+
Exceptions
Soluble
Slightly Soluble
Sodium,
S
di
potassium,
t
i
and
d
ammonium salts
Li+
Sodium, potassium, and
ammonium salts
Lithium, sodium, potassium,
and ammonium salts
(MgS, CaS, SrS, BaS, Al2S3
decompose in H2O)
Li+
+
+
Na and K
None
2+
Ca , Sr2+, Ba2+
Li+, Na+, K+, Ca2+, Sr2+, Ba2+
Oxides
(because they all react with H2O
to form soluble hydroxides!!!)
None
*
The term "soluble" means that the solubility is greater than about 1 g per 100 mL and "insoluble"
means that the solubility is less than 0.1 g per 100mL. Substances with solubility between these
limits are called in the table "slightly soluble".
**
Soluble in hot water.
20
A Double Displacement
Reaction:
( 3) 2
KI reacts with Pb(NO
in aqueous solution.
A yellow precipitate is
formed.
21
Solutions Before Mixing
At the moment of mixing
spectator ions (no change)
Reaction has occurred
(s)
22
Interpretation of a Double
Displacement Reaction
Complete Ionic Equation (CIE)
Pb2+(aq) + 2NO3 (aq) + 2K+(aq) + 2I  (aq) → PbI2(s) + 2K+(aq) + 2NO3 (aq)
spectator ions
Net Ionic Equation (NIE)
Pb2+(aq) + 2I  (aq) → PbI2(s)
23
Aqueous Solutions of Sodium Sulfate
and Barium Chloride Are Mixed
Acid-Base Reactions
24
Acid is a substance that increases
the concentration of H+ (or H3O+)
ions when it is dissolved in water.
Examples: HC2H3O2; HCl
Base is a substance that increases
the concentration of OH- ions when
it is dissolved in water.
Examples: KOH; NH3
Gas-Evolution Reactions
25
unstable
(molecular equation)
N.J. Tro, page 166
(net ionic equation)
26
Single Replacement Reactions
and Introduction to OxidationReduction Reactions
Single Replacement
Reactions
27
Zinc Metal Reacts with Hydrochloric Acid
28
Zinc Metal in Copper (II) Sulfate Solution
29
Iron Metal in Copper (II) Sulfate Solution
Copper Metal in Silver Nitrate Solution
30
Reducing
Agent (RA)
Oxidizing
Agent (OA)
In oxidation-reduction reactions
electrons are transferred from the atom
with less affinity for electrons to the
atom with more affinity for electrons.
31
OXIDATION IS LOSS of electrons
REDUCTION IS GAIN of electrons
OIL RIG
Terminology for Redox Reactions
32
Textbook page 271
33