1
Synthesis Reactions
Type 1: A metal combines with a
nonmetal to form a binary salt.
Example: A piece of lithium metal
is dropped into a container of
nitrogen gas.
6Li (s) + N2 (g) → 2Li3N (aq)
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Synthesis Reactions
Type 2: Metallic oxides and water
form bases (metallic hydroxides).
Example: Solid sodium oxide is added to
water
Na2O (s) + HOH (l) → 2NaOH (aq)
Example: Solid magnesium oxide is added to
water.
MgO (s) + 2HOH (l) → Mg(OH)2 (aq)
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Synthesis Reactions
Type 3: Nonmetallic oxides and
water form acids. The nonmetal
retains its oxidation number.
Example: Carbon dioxide is bubbled in water.
CO2 (g) + H2O (l) → H2CO3 (aq)
Example: Dinitrogen pentoxide is bubbled in
water.
N2O5 (g) + H2O (l) → 2HNO3 (aq)
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Synthesis Reactions
Type 4: Metallic oxides and
nonmetallic oxides form salts.
Example: Solid sodium oxide is added to
carbon dioxide.
Na2O (s) + CO2 (g) → Na2CO3 (aq)
Example: Solid calcium oxide is added to
sulfur trioxide.
CaO (s) + SO3 (g) → CaSO4 (aq)
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Decomposition Reactions
Type 1: Metallic carbonates
decompose into metallic oxides
and carbon dioxide
Example: A sample of magnesium
carbonate is heated.
MgCO3 (s) → MgO (s) + CO2 (g)
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Decomposition Reactions
Type 2: Metallic chlorates
decompose into metallic chlorides
and oxygen.
Example: A sample of magnesium
chlorate is heated.
Mg(ClO3)2 (aq) → MgCl2 (aq) + 3O2 (g)
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Decomposition Reactions
Type 3: Ammonium carbonate
decomposes into ammonia, water,
and carbon dioxide.
Example: A sample of ammonium
carbonate is heated.
(NH4)2CO3 (aq)→ 2NH3 (g) + H2O (l) + CO2 (g)
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Decomposition Reactions
Type 4: Sulfurous acid
decomposes into sulfur dioxide
and water.
Example: A sample of ammonium
carbonate is heated.
H2SO3 (aq) → H2O (l) + SO2 (g)
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Decomposition Reactions
Type 5: Carbonic acid
decomposes into carbon dioxide
and water.
Example: A sample of carbonic acid
is heated.
H2CO3 (aq) → H2O (l) + CO2 (g)
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Decomposition Reactions
Type 6: A binary compound may
break down to produce two
elements.
Example: Molten sodium chloride is
electrolyzed.
2NaCl (l) → 2Na (s) + Cl2 (g)
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Decomposition Reactions
Type 7: Hydrogen peroxide
decomposes into water and
oxygen.
Example: 2H2O2 (aq) → 2H2O (l) + O2 (g)
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Decomposition Reactions
Type 8: Ammonium hydroxide
decomposes into ammonia and
water.
Example: NH4OH (aq) → NH3 (g) + HOH (l)
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Single Replacement
Type 1: Active metals replace less
active metals from their
compounds in aqueous solution.
Example: Magnesium turnings are
added to a solution of iron (III)
chloride.
3Mg (s) + 2FeCl3 (aq)→ 2Fe (s) + 3MgCl2 (aq)
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Single Replacement
Type 2: Active metals replace
hydrogen in water.
Example: Sodium is added to water.
2Na (s) + 2HOH (l)→ 2NaOH (aq) + H2 (g)
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Single Replacement
Type 3: Active metals replace
hydrogen in acids.
Example: Lithium is added to
hydrochloric acid.
2Li (s) + 2HCl (aq) → 2LiCl (aq) + H2 (g)
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Single Replacement
Type 4: Active nonmetals replace
less active nonmetals from their
compounds in aqueous solution.
Example: Chlorine gas is bubbled
into a solution of potassium iodide.
Cl2 (g) + 2KI (aq) → I2 (g) + 2KCl (aq)
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Single Replacement
Type 5: If a less reactive element is combined
with a more reactive element in compound form,
their will be no resulting reaction.
Example: Chlorine gas is bubbled into a solution of
potassium iodide.
Cl2 (g) + KF (aq) → No Reaction
Example: Zinc is added to a solution of sodium
chloride.
Zn (s) + NaCl (aq) → No Reaction
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Double Replacement (Gas)
Common Gases
H2S
CO2
SO2
NH3
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Any sulfide (salt of S2-) plus any acid form H2S (g)
and a salt.
Any carbonate (salt of CO32-) plus any acid form CO2
(g), HOH, and a salt
Any sulfite (salt of SO32-) plus any acid form SO2 (g),
HOH, and a salt.
Any ammonium salt (salt of NH4+) plus any soluble
strong hydroxide react upon heating to form NH3 (g),
HOH, and a salt.
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Double Replacement (Gas)
• Example 1: The reaction of Na2SO3 and HCl
produces H2SO3:
Na2SO3 (aq) + 2HCl (aq) → H2SO3 (aq) + 2NaCl (aq)
• Bubbling is observed in this reaction because the
H2SO3 (sulfurous acid) is unstable and
immediately decomposes to give HOH and SO2
gas:
H2SO3 (aq) → HOH (l) + SO2 (g)
• The molecular equation for the overall or
complete reaction, therefore, is:
Na2SO3 (aq) + 2HCl (aq) → HOH (l) + SO2 (g) + 2NaCl (aq)
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Double Replacement (Gas)
• Example 2: A typical reaction of a carbonate
and an acid is:
K2CO3 (aq) + 2HNO3 (aq) → HOH (l) + CO2 (g) + 2KNO3 (aq)
• Bubbling is also observed in this reaction.
Theoretically H2CO3, carbonic acid, is formed,
but the acid is unstable and immediately
decomposes to form carbon dioxide gas and
water according to the following equation:
H2CO3 (aq) → HOH (l) + CO2 (g)
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Double Replacement (Gas)
• Example 3: Ammonium salts and soluble bases
react as follows (particularly when the solution is
warmed):
NH4Cl (aq) + NaOH (aq) → NH3 (g) + HOH (l) + NaCl (aq)
• The odor of ammonia gas is noted and moist blue
litmus paper held near the mouth of the container
will turn blue. Theoretically NH4OH, ammonium
hydroxide, is produced (also known as ammonia
water). The compound is unstable and
decomposes into ammonia gas and water:
NH4OH (aq) → NH3 (g) + HOH (l)
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Double Replacement (Gas)
• Example 4: The odor of rotten
eggs and bubbling are noted when
an acid is added to a sulfide. A
typical reaction producing
hydrogen sulfide gas is:
FeS (s) + 2HCl (aq) → FeCl2 (aq) + H2S (g)
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Acid-Base Reactions
• Example 1: Hydrogen sulfide
gas is bubbled through excess
potassium hydroxide solution.
H2S (g) + 2KOH (aq) → K2S (aq) + 2HOH (l)
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Acid-Base Reactions
• If the base is in excess, all hydrogen ions
will react with strong base to produce
water.
• Example 2: Dilute sulfuric acid is
reacted with excess sodium
hydroxide.
H2SO4 (aq) + 2NaOH (aq) → Na2SO4 (aq) + 2HOH (l)
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Acid-Base Reactions
• If however, this same reaction were described in terms
of mixing equal numbers of moles, then the coefficients
for both reactants would be one (the same number of H
and OH must be given away).
• Example 3: Equal number of
moles of sulfuric acid and sodium
hydroxide react.
H2SO4 (aq) + NaOH (aq) → NaHSO4 (aq) + HOH (l)
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Acid-Base Reactions
• As the following example demonstrates, it
is important to take into account the
quantity (concentration and amount) of each
reactant.
• Example 4: Equal volumes of 0.1 M
phosphoric acid and 0.2 M sodium
hydroxide are reacted together.
H3PO4 (aq) + 2NaOH (aq) → Na2HPO4 (aq) + 2HOH (l)
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