CHAPTER 7 REACTIONS IN WATER SOLUTIONS

1
CHAPTER 7 REACTIONS IN WATER SOLUTIONS Reactions
in water solution involve dissolved ionic
compounds and acids DISSOLVED IONIC
COMPOUNDS When an ionic compound dissolves in
water, the ions separate from each other
DISSOCIATION The separation of ions from an
ionic compound during the dissolving process
7A-1 (of 24)
2
NaCl (s)
NaCl (aq)
NaCl
?
Na Cl-
(s)
(aq)
(aq)
7A-2
3
MgBr2 (s)
MgBr2 (aq)
MgBr2
?
Mg2 2Br-
(s)
(aq)
(aq)
7A-3
4
Fe(NO3)3 (s)
Fe(NO3)3 (aq)
Fe(NO3)3
?
Fe3 3NO3-
(s)
(aq)
(aq)
7A-4
5
STRONG ELECTROLYTE A compound that dissolves in
water and produces many ions Water soluble ionic
compounds are strong electrolytes Electrolyte
solutions conduct electricity because the
dissolved ions are free to move throughout the
solution Strong electrolyte solutions conduct
electricity well
7A-5
6
PRECIPITATION REACTIONS
PRECIPITATE A solid formed when two solutions
are mixed
Dissolved ions that have a strong attraction for
each other will precipitate out of a solution
7A-6
7
5 SOLUBILITY RULES FOR DISSOLVED IONS IN DILUTE
SOLUTIONS
1 Group I and NH4 ions never precipitate out
of solution with anions
2 NO3- and C2H3O2- ions never precipitate out
of solution with cations
3 Cl-, Br-, and I- ions never precipitate out
of solution with cations except with Ag,
Hg22, or Pb2 ions
4 SO42- ions never precipitate out of solution
with cations except with Hg22, Pb2,
Ca2,Sr2, or Ba2 ions
5 CO32-, OH-, PO43-, and S2- ions do
precipitate out of solution with cations except
not with Group I and NH4 ions
7A-7
8
Determine if a precipitate will form if the
following solutions are mixed Mg(NO3)2 (aq)
and KBr (aq) No NaI (aq) and Pb(C2H3O2)2
(aq) Yes PbI2 (see Rule 3) Li2SO4 (aq)
and CaCl2 (aq) Yes CaSO4 (see Rule
4) (NH4)2CO3 (aq) and Ni(NO3)2 (aq) Yes
NiCO3 (see Rule 5)
7A-10
9
If two ionic solutions are mixed, a pair of ions
may combine to form a precipitate
AgNO3 (aq)
KCl (aq)
KNO3 (aq) AgCl (s)
7A-11
10
If two ionic solutions are mixed, a pair of ions
may combine to form a precipitate
AgNO3 (aq)
KCl (aq)
KNO3 (aq) AgCl (s)
7A-12
11
AgNO3 KCl
?
AgCl NaNO3
(aq)
(aq)
(s)
(aq)
MOLECULAR EQUATION
Ag(aq) NO3-(aq)
K(aq) 2Cl-(aq) ?
AgCl (s)
K(aq) NO3-(aq)
IONIC EQUATION
Ag(aq) Cl-(aq) ?
AgCl (s)
NET IONIC EQUATION
7A-13
12
Solutions of iron (II) chloride and sodium
hydroxide are mixed
Write in molecular form
FeCl2 NaOH ?
Fe(OH)2 NaCl
2
2
(aq)
(aq)
(s)
(aq)
Write in ionic form
Fe2(aq) 2Cl-(aq)
2Na(aq) 2OH-(aq) ?
Fe(OH)2 (s)
2Na(aq) 2Cl-(aq)
Write in net ionic form
Fe2(aq) 2OH-(aq) ?
Fe(OH)2 (s)
7A-14
13
Solutions of potassium sulfate and barium nitrate
are mixed
Write in molecular form
K2SO4 Ba(NO3)2 ?
KNO3 BaSO4
2
(aq)
(aq)
(aq)
(s)
Write in ionic form
2K(aq) SO42-(aq)
Ba2(aq) 2NO3-(aq) ?
BaSO4 (s)
2K(aq) 2NO3-(aq)
Write in net ionic form
SO42-(aq) Ba2(aq) ?
BaSO4 (s)
7A-15
14
Solutions of aluminum chloride and sodium
carbonate are mixed
Write in molecular form
Write in ionic form
Write in net ionic form
7A-16
15
ACIDS When dissolved in water, acid molecules
break apart into hydrogen ions and their
corresponding anions
IONIZATION The formation of ions from a
molecular compound during the dissolving process
7A-17
16
HCl (g)
HCl (aq)
HCl
?
H Cl-
(g)
(aq)
(aq)
(ionized form)
7A-18
17
STRONG ACID An acid in which all of the
molecules release hydrogen ions in water solution
HCl, HBr, HI, and oxyacids with at least 2 more
Os than Hs
HNO3
H2SO4
HClO4
H2CO3
Strong acids are strong electrolytes like soluble
ionic compounds because their solutions contain
many ions and conduct electricity well Strong
acids are written in ionized form in ionic
equations
7A-19
18
Solutions of hydroiodic acid and barium hydroxide
are mixed
Write in molecular form
HI Ba(OH)2 ?
H(OH) BaI2
2
(aq)
(aq)
(l)
(aq)
2
Write in ionic form
2H(aq) 2I-(aq)
Ba2(aq) 2OH-(aq) ?
2H2O (l)
Ba2(aq) 2I-(aq)
Write in net ionic form
2H(aq) 2OH-(aq) ?
2H2O (l)
H(aq) OH-(aq) ?
H2O (l)
7A-20
19
HF (g)
HF (aq)
HF ?

HF (aq)
(g)
(molecular form)
7A-21
20
WEAK ACID An acid in which all of the molecules
do not release hydrogen ions in water solution
All acids except HCl, HBr, HI, and oxyacids with
at least 2 more Os than Hs Weak acids are
written in molecular form in ionic equations
Weak acids are weak electrolytes because their
solutions contain small numbers of ions and
barely conduct electricity Weak acids are written
in molecular form in ionic equations
7A-22
21
Solutions of sulfurous acid and potassium
hydroxide are mixed
Write in molecular form
H2SO3 KOH ?
H(OH) K2SO3
2
(aq)
(aq)
(l)
(aq)
2
Write in ionic form
H2SO3 (aq)
2K(aq) 2OH-(aq) ?
2H2O (l)
2K(aq) SO32- (aq)
Write in net ionic form
H2SO3 (aq) 2OH-(aq) ?
2H2O (l) SO32- (aq)
7A-23
22
Solid copper (II) oxide is added to a solution of
hydrochloric acid
Write in molecular form
CuO HCl ?
CuCl2 H2O
2
(s)
(aq)
(aq)
(l)
Write in ionic form
CuO (s)
2H(aq) 2Cl-(aq) ?
H2O (l)
Cu2(aq) 2Cl-(aq)
Write in net ionic form
CuO (s) 2H(aq) ?
Cu2(aq) 2H2O (l)
7A-24