CHEMICAL REACTIONS IN
WATER
Section 4.6—CD-ROM Ch.
Ch. 4
We will look at
EXCHANGE
REACTIONS
AX + BY
The “driving force” is the formation of an
insoluble compound — a precipitate.
Pb(NO
Pb(NO3)2(aq)
aq) + 2 KI(aq
KI(aq)) ----->
2 KNO3(aq)
aq) + PbI2(s)
AY + BX
The anions
exchange places
between cations.
cations.
Precipitation Reactions
Pb(NO
Pb(NO3) 2(aq)
aq) + 2 KI(aq
KI(aq))
----> PbI2(s) + 2 KNO3 (aq
(aq))
Acid-Base Reactions
• A-B reactions are sometimes called
NEUTRALIZATIONS because the solution
is neither acidic nor basic at the end.
• The other product of the A-B reaction is a
SALT, MX.
HX + MOH ---> MX + H2O
Mn+ comes from base & Xn- comes from acid
This is one way to make compounds!
Net ionic equation
Pb2+(aq)
aq) + 2 I-(aq)
aq) ---> PbI2(s)
Acid-Base Reactions
• The “driving force” is the formation of
water.
NaOH(
NaOH(aq)
aq) + HCl(
HCl(aq)
aq) --->
NaCl(
NaCl(aq)
aq) + H2O(liq
O(liq))
• Net ionic equation
OH-(aq)
aq) + H+(aq)
aq)
---> H 2O(liq
O(liq))
• This applies to ALL reactions of
STRONG acids and bases.
GasForming
Reactions
Gas-Forming Reactions
• This is primarily the chemistry of metal
carbonates.
CO2 and water ---> H 2CO3
H2CO3(aq)
aq) + Ca2+ --->
2
H+(aq)
aq)
+ CaCO 3(s) (limestone)
Adding acid reverses this reaction.
MCO 3 + acid ---> CO 2 + salt
Page 1
CaCO3(aq)
aq) + H2SO4(aq)
aq) --->
2 CaSO4(s) + H2CO3(aq)
aq)
Carbonic acid is unstable and forms CO 2 & H2O
H2CO3(aq)
aq)
---> CO2 + water
(Antacid tablet has citric acid + NaHCO3)