Lesson 4.03/4.04
Single & Double
Replacement, Synthesis
and Decomposition
4.03
• Double Replacement Reaction: A type of
reaction in which the ions of two
compounds exchange places in an
aqueous solution to form two new
compounds.
AY + BZ → AZ + BY
Double Replacement Reactions:
1. A salt and a base
Ca(NO3)2 + 2 NaOH → 2NaNO3 + Ca(OH)2
4.03
2. Two Salts
2 KCl + Pb(NO3)2 → PbCl2 + 2KNO3
3. A Salt and an acid
Ba(NO3)2 + H2SO4 → BaSO4 + 2HNO3
4. Metal Carbonate and an acid
MgCO3 + 2HCl → MgCl2 + H2CO3
5. An acid and a base
2HCl + Mg(OH)2 → MgCl2 + 2H2O
4.03
Sample Problems:
1. KOH + H3PO4 →
2. FeS + HCl →
3. BaCl2 + K2CO3 →
4.03
• Single Replacement Reaction : one
element reacts by replacing another
element in a compound.
A + BY → AY + B
To predict whether a single replacement
reaction will occur, and what its products
will be, you must compare the individual
element to the similar element within the
compound to determine if the replacement
can occur.
4.03
• The activity series of metals can help you
identify single replacement reactions and
predict the products that will form.
• Activity Series of Metals
Li, Rb, K, Ba, Sr, Ca, Na, Mg, Al, Mn, Zn, Cr,
Fe, Cd, Co, Ni, Sn, Pb, H2, Sb, Bi, Cu, Hg, Ag,
Au
* In an activity series list, elements are listed from
most reactive to least reactive. On the list above,
lithium (Li) is most reactive, where gold (Au) is
least reactive.
4.03
Single Replacement Reactions:
1. A metal replacing a less active metal
2Na + CuSO4 → Na2SO4 + Cu
Sodium can replace copper in the compound
because Na is higher on the activity series than
Cu.
Zn + NaCl → no reaction
Zinc cannot replace sodium because Zn is lower on
the activity series than Na.
4.03
2. A metal replacing the hydrogen in water
• The highly reactive metals (such as the alkali
metals in Group 1) react vigorously with water to
produce a metal hydroxide and hydrogen gas.
2Na + 2H2O → 2NaOH + H2
• Less active metals, such as aluminum and iron,
can react with water under the right conditions to
produce a metal oxide and hydrogen gas.
Zn + H2O → ZnO + H2
Au + H2O → no reaction
4.03
The halogens decrease in reactivity as you go down
the group.
F2 + 2NaCl → 2NaF + Cl2
Sample Problems:
1. Ca + H2O →
2. Zn + FeSO4 →
3. Br2 + CaCl2 →
4.03
3. A metal replacing the hydrogen in an acid
• The more reactive metals can react with certain
acids, such as hydrochloric acid and sulfuric acid,
to form an ionic compound (a salt) and hydrogen
gas.
Pb + 2HCl → PbCl2 + H2
4. A nonmetal replacing a less active
nonmetal
• A nonmetals get involved in the replacement as
well. A halogen in Group 17 can take the place of
a less active halogen within a compound.
4.04
• Synthesis Reaction: involve two or more
reactants combining to form one new
substance.
A + B → AB
Synthesis Reactions:
1. Nonmetal oxide with water = oxyacid
SO3 + H2O → H2SO4
2. Metal oxide with water = metal hydroxide
CaO + H2O → Ca(OH)2
3. Metal with nonmetal = neutral compound
4.04
Ca + Cl2 → CaCl2
4. Nonmetal and oxygen = nonmetal oxide
S + O2 → SO2
5. Metal oxide and nonmetal oxide = salt
MgO + SO2 → MgSO3
Sample Problems:
1. N2 + O2 →
4.04
2. Na + Cl2 →
3. MgO + H2O →
• Decomposition Reaction: starts with only
one reactant but ends with more than
one product.
AB → A + B
Decomposition Reactions:
4.04
1. Binary compound = 2 individual elements
2H2O → 2H2 + O2
2NaCl → 2Na + Cl2
2. Metal carbonate = metal oxide + CO2
CaCO3 → CaO + CO2
3. Metal chlorate = metal chloride + O2
2KClO3 → 2KCl + 3O2
4. Metal hydroxide – metal oxide + water
Ca(OH)2 → CaO + H2O
4.04
5. Oxyacids - nonmetal oxides + water
H2SO4 → SO3 + H2O
Sample Problems:
1. Ca(ClO3)2 →
2. H2CO3 →
3. Na2CO3 →