Determining Products of Reactions
• To predict the products for any equation, you must first determine
• Synthesis –
• Decomposition –
• Combustion –

• 2 or more reactants and you’re told that there’s only one product =
• When writing the products, you must look at the charges of the ions.
• Example: Al
(s)
+ Br
2(l)

• Example: Ca
(s)
+ N
2(g)


• 1 reactant = decomposition
• Remember the “7” diatomic molecules and
• Example: CCl
4(l)

• Example: Mg
3
N
2(s)


• hydrocarbon (compound with C & H) + O
2
=
• Example: CH
4(g)
+ O
2(g)

• Example: C
3
H
8
O
(g)
+ O
2(g)


• C
8
H
18
+ O
2

• Ba(NO
3
)
2

• Mg + O
2


• Single displacement – 1 element & 1 compound react
• Double displacement – 2 compounds react
• Neutralization – acid and base in the reactants

• 1 element & 1 compound =
• In the products, you can’t have
• Example: Mg
(s)
+ Zn(NO
3
)
2(aq)

• Example: Cl
2(g)
+ KF
(aq)


• 2 ionic compounds =
• Example:
AgNO
3(aq)
+ NaCl
(aq)

• Example:
Fe
2
(SO
4
)
3(aq)
+ Na
3
PO
4 (aq)


• 1 acid (starts with H) & 1 base (ends with OH) =
• Water gets rid of all hydrogen and hydroxide ions.
• Example: HCl
(aq)
+ KOH
(aq)

• Example: Ca(OH)
2(aq)
+ H
2
SO
4(aq)


• If a substance is an aqueous solution (aq),
• If a substance is insoluble,
• Insoluble substances form as the result of
• If a substance is slightly soluble or partially soluble in water,

Figure 7.3:
Solubilities of common compounds.

• Ca(NO
3
)
2
• CuOH
• CaCl
2
• (NH
4
)
2
SO
4
• Zn
3
(PO
4
)
2
• FeCO
3
• SrO

• in all precipitation reactions,
• At least one of the products formed is
K +
KI(aq) + AgNO
3
(aq)

KNO
3
(aq) + AgI
 s

Ag + K +
Ag I
I -
NO
3
NO
3
-

• Occurs in ionic compounds and acids
• when ionic compounds dissolve in water the anions and cations are separated from each other; this is called dissociation
• we know that ionic compounds dissociate when they dissolve in water because the solution conducts electricity

Electrical conductivity of aqueous solutions. (a) Pure water does not conduct an electric current. (b) When an ionic compound is dissolved in water, current flows and the lamp lights.

Figure 7.5: When gaseous HCl is dissolved in water, each molecule dissociates to produce H + and Cl ions.

• potassium chloride dissociates in water
KCl(aq) = K + (aq) + Cl (aq)
K Cl K + Cl -
• copper(II) sulfate dissociates in water
CuSO
4
(aq) = Cu +2 (aq) + SO
4
2(aq)
Cu SO
4
Cu +2 SO
4
2-

• potassium sulfate dissociates in water
K
2
SO
4
(aq) = 2 K + (aq) + SO
4
2(aq)
K +
K SO
4
K
SO
4
2-
K +

Process for Predicting the Products of a Precipitation Reaction
• Determine what ions
• Exchange Ions
– (+) ion from one reactant with (-) ion from other
• Balance Charges of combined ions to
• Balance the Equation
– count atoms
° Determine Solubility
– solubility rules
– if product is insoluble or slightly soluble,

Figure 7.1:
The precipitation reaction that occurs when yellow potassium chromate,
K
2
CrO
4
(aq), is mixed with a colorless barium nitrate solution,
Ba(NO
3
)
2
(aq).

Figure 7.4:
Precipitation of silver chloride occurs when solutions of silver nitrate and potassium chloride are mixed.

• Predict the products given each of the following reactants. Also denote which compound forms a precipitate:
Cu(NO
3
)
2(aq)
+ KOH
(aq)

FeCl
3(aq)
+ Mg
3
(PO
4
)
2(aq)

NaBr
(aq)
+ AgNO
3(aq)
