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CHEMICAL REACTIONS
The process by which one or more substances are changed into one or more different substances
Equations
Reactions are represented by a chemical equation
Reactants Products
Must have the same number and type of atoms on
both sides of the equation
Synthesis Reactions
Two reactants produce one product Examples:
NH3 + HCl NH4Cl
H2 + O2 H2O
Ag + S Ag2S
Al + Cl2 AlCl3
Decomposition
One reactant produces two products Examples
Ag2O Ag + O2
PCl5 PCl3 + Cl2
H2O2 H2O + O2
CuO Cu + O2
Single Displacement
One element and one compound producing a different element and compound
Examples
Fe + H3(PO4) H2 + Fe3(PO4)2
H2 + CuO Cu + H2O
Zn + HCl H2 + ZnCl2
Cl2 + KBr Br2 + KCl
Double Displacement
Two compounds producing two different compounds
Examples:
Al(NO3)3 + NaOH Al(OH)3 + NaNO3
PbCl2 + Li2SO4 PbSO4 + LiCl
ZnBr2 + AgNO3 Zn(NO3)2 + AgBr
BaCl2 + KIO3 Ba(IO3)2 + KCl
Combustion
A hydrocarbon reacts with oxygen to produce
carbon dioxide and water
Examples:
CH4 + O2 CO2 + H2O
C6H12O6 + O2 CO2 + H2O
Chemical Equations from Names
magnesium and hydrogen chloride produce hydrogen and magnesium chloride
calcium hydroxide and lithium chloride produce lithium hydroxide and calcium chloride
decompose copper (II) oxide into copper and oxygen
aluminum and iron (III) oxide produce iron and aluminum oxide
combustion of butane (C4H10) in air to produce carbon dioxide and water
Predicting the Product - Rules
1. If hydrocarbon reacts with oxygen combustion
reaction
i. The products will be CO2 and H2O.
2. If two elements or very simple molecules combine
synthesis reaction.
i. The products will be predictable using the rules of
ionic bonding.
Predicting the Product – More Rules
3. If starting with one compound decomposition
reaction.
i. The products will be very simple molecules, or some
elements, or both.
a. Remember the rules for metals and non-metals
4. If a pure element reacts with another compound
(usually ionic) single displacement reaction.
i. The pure element (cation) switches places with
another element (cation) in the other compound.
Predicting the Product – More Rules
5. If two ionic compounds combine double
displacement reaction.
i. Switch the cations and balance out the charges to
figure out what will be made.
Predict the Product - Practice
Magnesium and nitrogen
Copper II oxide is decomposed into its elements
Chlorine and potassium bromide
Calcium hydroxide and hydrogen sulfate
Iron (III) chloride and sodium hydroxide
Methane is combusted in air
Precipitate
Precipitation is the formation of a solid in a solution
or inside another solid during a chemical reaction
the solid formed is called the precipitate
SOLUBILITY RULES
All common salts of Group I elements and
ammonium are soluble
All common acetates and nitrates are soluble
All binary compounds of Group 7 (other than F)
with metals are soluble except those of silver,
mercury I and lead
More Solubility Rules
All sulfates are soluble except those of barium,
strontium, calcium, silver, mercury I and lead
Except for those in Rule 1, carbonates, hydroxides,
oxides, sulfides and phosphates are insoluble
Precipitate Reaction
General form: AB(aq) + CD(aq) → CB(s) + AD(aq)
Description: In a precipitation reaction two solutions
are mixed together to produce an insoluble solid
which is called the precipitate.
This type of reaction is also called a double
displacement reaction
Physical States of Matter and Symbols
All physical states are given at standard
temperature and pressure for each chemical
species.
(aq) = aqueous solution (dissolved in water, from aqua
or water).
(l) = liquid
(s) = insoluble solid or precipitate.
(g) = gas
Precipitate Reactions
General form: AB(aq) + CD(aq) → CB(s) + AD(aq)
Is a double displacement reaction!!
Examples
Lead nitrate(aq) + Potassium iodide(aq) → Lead iodide(s) + potassium nitrate(aq)
Pb(NO3)2(aq) + 2KI(aq) → PbI2(s) + KNO3(aq)
Silver nitrate(aq) + sodium chloride(aq) →Silver chloride(s) + sodium nirate(aq)
AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)
Mercury(II) nitrate(aq) + Potassium iodide(aq) → Mercury iodide(s) + Potassium nitrate
Hg(NO3)2(aq) + 2KI(aq) → HgI2(s) + KNO3(aq)
Barium chloride(aq) + Sodium sulfate(aq) → Barium sulfate(s) + Sodium chloride(aq)
BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + NaCl(aq)
Copper sulfate(aq) + Sodium hydroxide(aq) → Copper hydroxide(s) + Sodium sulfate(aq)
CuSO4(aq) + 2NaOH(aq) → Cu(OH)2(s) + Na2SO4(aq)
What are Net Ionic Equations?
Equations that show only the soluble, strong
electrolytes reacting (ions) and omit the spectator
ions, which go through the reaction unchanged.
Bare bones of the chemical reaction
Usually take place in aqueous environments
Ions separate in water into cations and anions
Net Ionic Equations – in words
1. Write the (balanced!) molecular equation first
Reaction products: swap cations and anion
Predict solubility (using Solubility rules)
Net Ionic Equations – in words
2. Write the complete ionic equation next
(s) compounds don’t ionize
(aq) compounds do ionize
ion subscripts in the molecular equation become
coefficients in the complete ionic equation
Ie (NO3)2 becomes 2(NO3)
Net Ionic Equations – in words
3. Write the net ionic equation next
cancel spectator ions
The net ionic equation is a “simplified” form
of the complete ionic equation
Net Ionic Equations
Balanced Chemical Equation:
Pb(NO3)2(aq) + 2NaI(aq) PbI2(s) + 2NaNO3(aq)
“Complete Ionic” Equation:
Pb2+(aq) + 2NO3
-(aq) + 2Na+
(aq)+ 2I-(aq) PbI2(s) + 2Na+(aq) + 2NO3
- (aq)
Cancel the “spectator ions” that appear on both sides of the arrow
Pb2+(aq) + 2NO3
-(aq) + 2Na+
(aq)+ 2I-(aq) PbI2(s) + 2Na+(aq) + 2NO3
- (aq)
“Net Ionic” Equation:
Pb2+(aq) + 2I-(aq) PbI2(s)
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