Transcript Reaction Predictions - MallardCreekChemistry

Reaction Predictions
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Most Commonly Used
Cations
and
Anions
+
Hydrogen H
Sodium Na+
Potassium K+
Calcium Ca+²
Magnesium Mg+²
Iron (Ferrous)
Fe+²
Iron (Ferric) Fe+³
•Hydroxide OHˉ
•Chloride Clˉ
•Sulfide Sˉ²
•Bicarbonate HCOзˉ
•Carbonate COзˉ²
•Sulfate SO4ˉ²
•Phosphate PO4ˉ³
Cations/ Anions, contd.
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You can figure out the charge of an
ion by using the periodic table. For
Example:
Alkali metals such as Lithium can
easily lose an electron to become
stable (just like a Noble gas) so taking
away an electron give Lithium a +1
charge.
On the other hand Halogens can easily
accept an electron to become stable.
Practice
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What is the oxidation state of Oxide?
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What is the oxidation state of Iodide?
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What is the oxidation state of a
Calcium ion?
What is the oxidation state of a
Answers
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-2
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-1
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+2
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+1
Net Ionic Equation
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To create a net ionic equation, you
break apart all ionic molecules in a
balanced molecular equation into their
ions if they are soluble.
If there are spectator ions, ions that
appear on both sides of the equation,
they cancel each other.
Net Ionic Example
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Silver nitrate is mixed with potassium
chromate
– 2AgNO3 + K2CrO4 → Ag2CrO4 + 2KNO3
Molecular Equation
– 2Ag+ + 2NO3ˉ + 2K+ + CrO4-2 → Ag2CrO4
+ 2K+ + 2NO3-2
Complete ionic equation
– 2Ag+ + CrO4-2 → Ag2CrO4
Net Ionic Equation
Solubility Rules
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NO3
all nitrates are soluble
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CH3COO or C2H3O2
all acetates are soluble except AgCH3COO
ClO3
all chlorates are soluble
Cl all chlorides are soluble except AgCl, Hg2Cl2,
PbCl2
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Br all bromides are soluble except AgBr, PbBr2,
Hg2Br2, and HgBr2
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I all iodides are soluble except AgI, Hg2I2, HgI,
and PbI2
Solubility Rules, contd.
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SO4¯² all sulfates are soluble except
BaSO4, PbSO4, Hg2SO4, CaSO4,
AgSO4 and SrSO4
Alkali metal, cations, and NH4 – all are
soluble
H+ all common inorganic acids and
low molecular mass organic acids are
soluble
(In)Soubility Rules,
contd.
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-
CO3 ²
all carbonates are insoluble except those
of alkali metals and NH4
CrO4 ²
all chromates are insoluble except those
of alkali metals, NH4, CaCrO4, and SrCO4
OH
all hydroxides are insoluble except those
of the alkali metals, NH4, Ba(OH)2, Sr(OH)2, and
Ca(OH)2
PO4 ³
all phosphates are insoluble except those
of alkali metals and NH4
SO3 ²
all sulfites are insoluble except those of
alkali metals and NH4
S ²
all sulfides are insoluble except those of
alkali metals and NH4
Synthesis
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Synthesis occurs when two or more reactants
combine to form a single product. There are several
common types of synthesis reaction.
You know it happens when you have:
-A metal combines with a nonmetal to form a
bianary salt.
-A piece of lithium metal is dropped into a
container of nitrogen gas.
6Li+ N2  2Li3N
-Metal oxide and water forms a base (metallic
hydroxide)
-Solid sodium oxide is added to water.
Synthesis, contd.
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Nonmetal oxide and water forms
acids. Nonmetal retains its oxidation
number.
-Carbon dioxide is burned in water.
CO2 + H2O  H2CO3
Metallic oxides and nonmetallic
oxides form salts.
-Solid sodium oxide is added to
carbon dioxide.
Na O + CO  Na CO
Decomposition
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Occurs when a single reactant is
broken down into two or more
products.
The reactions react to form basic
compounds or elements.
When a compound is heated or
electrolyzed, it means that it is broken
up into its ions.
AB A+B
Examples of
Decomposition
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A sample of magnesium carbonate is
heated.
MgCO3  MgO + CO2
Molten sodium chloride is electrolyzed.
2NaCl  2Na + Cl2
A sample of ammonium carbonate is
heated.
(NH4)2CO3  2NH3 + H2O + CO2
Single Replacement
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Reactions that involve an element
replacing one part of a compound. The
products include the displace element
and a new compound. An element can
only replace another element that is
less active than itself. (Look a activity
series/ AP packet)
A +BX B+AX
Single Replacement
Rules
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Active metals replace less active
metals from the less active metals’
compounds in aqueous solutions
ex. 3Mg+ 2FeCl3—> 2Fe + 3MgCl2
Active metals replace hydrogen in
water
ex. 2Na + 2H2O—> H2 + 2NaOH
Active metals replace hydrogen in
acids
Single Replacement
Rules, contd.
4. Active nonmetals replace less active
nonmetals from their compounds in
aqueous solutions
ex. Cl2 + 2KI —> I2 + 2KCl
5. If a less reactive element is combined
with a more reactive element in
compound form, there will be no
reaction
ex. Cl2 + KF —> no reaction*
* On the AP test reactions will ALWAYS
Activity Series (Single
Replacement)
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Metals
– Li, Ca, Na, Mg, Al, Zn, Fe, Pb, [H2], Cu, A
g, Pt
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Nonmetals
– F2, Cl2, Br2, I2,
More active

Less Active
Double Replacement
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Two compounds react to form two new
compounds. No changes in oxidation numbers
occur.
Each cation pairs up with the anion in the other
compound.
The “driving force” in these reactions is the removal
of at least one pair of ions from solution.
This removal of ions happens with the formation of
a precipitate, gas, or molecular species.
When a double replacement reaction doesn’t go to
completion, it is a reversible reaction (no ions have
been removed).
AX+ BY  AY+ BX
How do you know a double
replacement reaction occurs?
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The reactants will contain a(n):
-gas
-insoluble precipitate
-molecular species
*Remember– on the AP test the reaction
will always occur
Common Gases Released (Dbl.
Repl.)
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H2S Any sulfide plus any acid forms
H2S and a salt.
CO2 Any carbonate plus any acid form
CO3, water, and a salt.
SO2 Any sulfite plus any acid form
SO2,
water, and a salt.
NH3 Any ammonium plus a soluble
hydroxide form NH3, water, and a
salt.
Acid/ Base Reactions
(Dbl. Repl.)
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An acid and a base will react and form
water and a salt.
Hydrochloric acid is added to sodium
hydroxide.
HCl + NaOH  NaCl + H2O
Hydrolysis (Dbl. Repl.)
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It is the reverse of neutralization and results when a salt plus a water
molecule yields an acid plus a base.
Salt + water  acid + base
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Key things to know about hydrolysis reactions:
– Salts of a strong acid plus a weak base will hydrolyze into an acidic
solution.
NH4+ +Cl- +H2O → H+ +Cl- + (NH)4OH
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– Salts of a weak acid and a strong base will always hydrolyze to give a
basic solution.
+
K +F- +H2O → K+ +OH- +HF
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– Salts of a strong acid and a strong base will never undergo hydrolysis
and therefore make a neutral solution.
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Na +Cl- +H2O → Na+ +OH- +H+ Cl-
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– Salts of a weak acid plus salts of a weak base may hydrolyze as an acid,
base, or a neutral solution; the final result depends on the Ka’s and Kb’s
of the acids and bases formed during the hydrolysis process.
Disclaimer!! The spectator ions were not removed 
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Examples of Dbl.
Replacement
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Solutions of potassium bromide and
silver nitrate are mixed.
KBr + AgNO3  AgBr + KNO3
A solution of sodium sulfate is added
to a solution of hydrochloric acid.
Na2SO3 + 2HCl  2NaCl +
H2SO3
Hydrolysis Sample
Problems
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Try these:
– An aqueous solution of manganese (II)
sulfate undergoes hydrolysis.
– Ammonium fluoride and water are mixed
together.
Hydrolysis answers
– MnSO4 + 2H2O → H2SO4 + Mn(OH)2
– NH4F + H2O → HF + NH4OH
Combustion (Organic
Reacs.)
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An organic compound reacts with O2 to
form water and carbon dioxide.
If something is burned there is a
combustion reaction.
Methanol is burned in oxygen gas.
2CH3OH + 3O2  4H2O + 2CO2
Addition (Organic
Reacs.)
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A halogen or hydrogen is added to an
alkene or alkyne, breaking apart the
double or triple bonds and forming
single bonds.
Fluorine is added to ethene
F2 + CH2=CH2  CH2F-CH2F
Substitution (Organic
Reacs.)
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An atom attached to a carbon is
removed and something else takes its
place.
Bromine is added to methane
Br2 + CH4  CH3Br + HBr
Oxidizing Agents (Redox
Reacs.)
Common Oxidizing Agents
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MnO4¯ in acidic solution
MnO2 in acidic solution
MnO4¯ in neutral or basic solution
Cr2O7ˉ² in acidic solution
HNO3, concentrated
HNO3, dilute
H2SO4, hot, concentrated
Metallic ions (higher oxidation #)
Free halogens
Na2O2
HClO4
C2O4ˉ²
H 2O2
Products Formed
Mn+²
Mn+²
MnO2(s)
Cr+³
NO2
NO
SO2
Metallous ions (lower oxidation #)
Halide ions
NaOH
Clˉ
CO2
O2
Reduction Agents (Redo
Reacs.)
Common Reducing Agents
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Halide ions
Free metals
Sulfite ions or SO2
Nitrite ions
Free halogens, dilute
basic solution
Free halogens,
concentrated basic
solution
Metallous ions (lower
oxidation #)
Products Formed
Free halogen
Metal ions
Sulfate ions
Nitrate ions
Hypohalite ions
Halite ions
Metallic ions
(higher oxidation #)
Electrolysis (Redox
Reacs.)
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An electrolysis reaction is a reaction in which a nonspontaneous redox reaction is brought about by the
passage of current under sufficient external
electrical potential. The devices in which electrolysis
reactions occur are called electrolytic cells.
In theory, E° values (Standard Reduction
Potentials) can be used to predict which element
will plate out at a particular electrode when various
solutions are combined.
(B&L text)
Rules for Predicting Cathode
Reactions (Reduction)
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When a direct electric current is passed
through a water solution of an electrolyte,
two possible reduction processes may
occur at the cathode.
The cation may be reduced to the
corresponding metal.
Mn+ + ne-  M(s) (reaction 1)
n = (charge of cation)
Water molecule may be reduced to
elementary hydrogen
2H2O + 2eˉ  H2 + 2OHˉ (reaction 2)
Rules for Predicting Cathode
Reactions, contd.
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For salts containing transition metal cations,
which are relatively easy to reduced
compared to water, reaction #1 will occur at
the cathode (and the transition metal will
plate out).
Mn+ + ne-  M(s)
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If the cation is representative metal, the
water molecules will be easier to reduce
compared to the cation, and reaction #2 will
occur at the cathode, producing hydrogen
gas and hydrogen ions.
2H2O + 2eˉ  H2 + 2OHˉ
Rules for Predicting Anode
Reaction (oxidation)
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The oxidation process that occurs at the anode of
an electrolytic cell operating in aqueous solution
may be one of two oxidation processes.
The anion may be oxidized to the corresponding
nonmetal.
- 2Xˉ  X2 + 2eˉ (reaction 1)
Water molecules may be oxidized to elementary
oxygen.
- HOH  ½ O2 + 2H+ + 2eˉ (reaction 2)
Rules for Predicting
Anode Reactions, contd.
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For salts containing iodide, bromide, or
chloride ions, it is usually easier to oxidize
these nonmetals rather than water. It will
be found that the nonmetal is formed at the
anode.
When the anion present is any other ion
that is more difficult to oxidize than water,
Reaction #2 will occur at the anode
producing elementary oxygen and aqueous
hydrogen ions.
Example Electrolysis
Reactions
Copper (II) chloride in water
Cu+2 + 2Clˉ  Cu + Cl2
2. Copper (II) sulfate in water
Cu+2 + HOH  Cu + ½ O2 + 2H+
3. Sodium chloride in water
2Clˉ + 2HOH  H2 + Cl2 + 2OHˉ
4. Sodium sulfate in water
2HOH  2H2 + O2
1.
Metals w/ Multiple Oxidation
Levels (Redox Reacs.)
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These metals can change their oxidation state in a redox reaction
– Antimony (III) or (V)
– Bismuth (III) or (IV)
– Cerium (III) or (IV)
– Chromium (II) or (III)
– Cobalt (II) or (III)
– Copper (I) or (II)
– Gallium (I) or (II) or (III)
– Germanium (II) or (IV)
– Gold (I) or (III)
– Iron (II) or (III)
– Lead (II) or (IV)
– Mercury (I) or (II)
– Nickel (II) or (III)
– Thallium (I) or (III)
– Thorium (II) or (IV)
– Tin (II) or (IV)
Complex Ion Reactions
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Nomenclature is on pages 23-27 of The Ultimate
Chemical Equations Handbook
There are a lot of very complicated types of these
reactions, but, for all intensive purposes and for the
AP test, you only need to be familiar with those
reactions pertaining to ammonia and water.
In a complex ion reaction, ligands will attach to a
transition metal ion.
There will usually be twice as many ligands as the
metals oxidation number
Complex Ion Reactions,
contd.
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These reactions usually occur in a
concentrated solution of the ligand.
Copper chloride (II) is added to a
concentrated solution of ammonia
– Cu2+ +NH3  [Cu(NH3)4]2+
Common Reaction
Terms
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Electrolysis: Electricity is run through a compound,
resulting in a change of oxidation states.
Hydrolysis: The reaction of a salt with water to
form molecular species. Salts of a strong acid + a
weak base will always hydrolyze to give an acidic
solution.
Neutralization: Acid and base react to form a salt
and water.
Catalyst: A molecule that speeds that speeds a
reaction but that does not appear in the reaction.
Oxidation number: the charge that it would have if
all the ligands (atoms that donate electrons) were
removed along with the electron pairs that were
shared with the central atom
Common Reaction
Terms, contd.
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Precipitate: an insoluble substance
formed by the reaction of two aqueous
substances.
Anode: the electrode where oxidation
occurs
an ox
Cathode: the electrode where
reduction occurs
red cat