Download + H 2 O(g)

Chemical
Reactions
Chemical Reaction
the process by which
one or more substances
are changed into one or
more different
substances
REACTANTS
the starting substances in
a chemical reaction
(the stuff on the left)
PRODUCTS
the final substances in a
chemical reaction
(the stuff on the right)
General Formula
for Reactions
A+B C
Reactants yields Products
Law of Conservation
of Mass/Matter
Mass/Matter can not be
created nor destroyed,
simply changed from 1
form to another
EQUATIONS
CH4 + 2O2
CO2 + 2H2O
REPRESENTATION OF
PHYSICAL STATES IN
EQUATIONS
You may see these in book problems
• (g) = gas
• (l) = liquid
• (cr) = solid (stands for crystalline)
• (aq) = substance dissolved in water
WRITING BALANCED
EQUATIONS
• STEP 1: Write all of the atoms in the
reactants and the products (in the same order)
• STEP 2: Put * next to the atom in step 1, if an
element occurs more than once on one side of
a reaction
• STEP 3: Balance the equation (get the same #
of atoms of each element on each side). You
can only do this by changing coefficients!
WARNING!!!
Never
Ever
Ever
CHANGE THE SUBSCRIPT
Hints for Balancing
• Balance metals first
• Then balance polyatomics
• Then balance non-metals
• Last, balance hydrogens
Hints for Balancing
• If an element is by itself,
balance it last
• Watch for even or odds,
balance accordingly
• Don’t forget your diatomics
in transcribed problems
Hints for Balancing
•
balance anything that is
found in 1 product/reactant
st
1 ,
• Then, balance anything that
is found in 2 or more
products / reactants
Reaction of Zinc with HCl
Please balance the equation
__Zn + __HCl  __ZnCl2 + __H2
Zn = 1
Zn = 1
H=1
H=2
Cl = 1
Cl = 2
Combustion of ethane C2H6
Please balance the equation
__C2H6 + __O2  __CO2 + __H2O
C=2
C=1
H=6
H=2
O=2
*O = 3
Zinc + Hydrochloric Acid
Please write the reaction
Writing Balanced Equations
When Given Words Only
• STEP 1: Write out the symbols
• STEP 2: Balance your charges
(if needed)
• STEP 3: Check for diatomics
• STEP 4: Balance Equation
Hints for Balancing
Don’t forget your diatomics
in transcribed problems
• Don’t forget to Kriss Kross
and use ( )
Combustion of Acetone
(CH3)2CO
Please write the reaction
(CH3)2CO(l) + O2(g)  CO2(g) + H2O(g)
HOMEWORK
Pg. 228 #1-12
Pg. 243 #43, 45, 46, 58
Worksheet
SYNTHESIS
two or more
substances combine
to form one new
substance
SYNTHESIS
A + B  AB
Na + Cl2  NaCl
Pb(IV) + O2 
Pb2O4
Info on Synthesis Reactions
• Also known as “combination”
reactions
• Always form compounds
• Generally give off lots of energy
• Can be reversed (decomposition)
•
DECOMPOSITION
when a substance
breaks up into
simpler substances
Decomposition
AB  A + B
NaCl  Na + Cl2
Pb2O4  Pb + O2
Info on Decomp Reactions
• Energy is usually need to make
these reactions happen
• Often hard to predict products
unless the substance breaks into its
ionic components (or memorize
some basic types of reactions)
• Often are the cause of explosions
Types Decomp Reactions
Metallic Carbonates
• When heated, metallic carbonates
decompose into metallic oxides and
carbon dioxide
• BaCO3 --> BaO + CO2
• Cu2CO3 --> Cu2O + CO2
Types Decomp Reactions
Metallic Chlorates
• When heated, metallic chlorates
decompose into metallic chlorides
and oxygen
• KClO3 --> KCl + O2
• Zn(ClO4)2 --> ZnO + O2
Types Decomp Reactions
Metallic Hydroxides
• When heated, metallic hydroxides
decompose into metallic oxides and
water
• Ca(OH)2 --> CaO + H2O
• Mn(OH)4 --> Mn2O4 + H2O
Types Decomp Reactions
Metallic Oxides
• When heated, metallic oxides
decompose into the metal and
oxygen
• K2O --> K + O2
• Pb2O4 --> Pb + O2
Decomp of Trinitrotoluene
2C7H5N3O6 (s) -->
3N2(g) + 7CO2(g) + 5H2O(g) + 7C(s)
• 2 moles of TNT decompose to produce 15 moles of
hot, expanding gases…that is why it is so
powerful!
SINGLE
DISPLACEMENT
one element
displaces another
in a compound
Single Displacement Reaction
Single Displacement
AB + C  AC + B
or CB + A
NaBr + Cl2  NaCl + Br2
(NH4)2S + O2  (NH4)2O + S
Info on Single Replacement
• Also known as single displacement
reactions
• Only elements with a higher activity
can replace other elements (use table
on pg. 217)
• Nonmetals can replace other nonmetals, but is usually limited to
halogens (active decreases down table)
Types Single Replacement
Metals
• More active metal atoms will
replace less active metal ions from
compounds
• Cu + AgNO3 --> Ag + Cu(NO3)2
• Ag + Cu(NO3) --> No Reaction
Types Single Replacement
Halogens
• More active halogen atoms will
replace less active halogen ions
from compounds
• F2 + NaCl --> Cl2 + NaF
• Cl2 + FCl --> No Reaction
Types Single Replacement
Halogens
• More active halogen atoms will
replace less active halogen ions
from compounds
• F2 + NaCl --> Cl2 + NaF
• Cl2 + FCl --> No Reaction
DOUBLE
DISPLACEMENT
the positive or
negative portions of
two compounds are
switched
Double Displacement
AB + CD  AD + CB
NaBr + Pb2S3  Na2S + PbBr3
K2SO4 + Ba(OH)2 KOH + BaSO4
Info on Double Replacement
• Also known as double displacement
reactions
• Reactants must be two ionic compounds in
aqueous solution
• Cations switch positions
• Usually produces a precipitate (ppt)
For Double Replacement to
Occur one is Usually True
• Also known as double displacement
reactions
• Reactants must be two ionic compounds in
aqueous solution
• Cations switch positions
• Usually produces a precipitate (ppt)
COMBUSTION
(aka OXIDATION)
hydrocarbon reacts
with oxygen to form
carbon dioxide and
water
Writing Out Equations
• STEP 1: Determine type of rxn
• STEP 2: Write out symbols
• STEP 3: Kriss-Kross where
necessary
• STEP 4: Diatomics
• STEP 5: Balance the equation
Common Words
• Decomposes = breaks apart
• Combusts = a combustion rxn
• Reacts with = A + B
• “To form” or “to get”= 
• Yields = 
• Displaces = have a single D. rxn
• And = plus (+)
Common Words
• Decomposes = breaks apart
• Combusts = a combustion rxn
• Reacts with = A + B
• “To form” or “to get”= 
• Yields = 
• Displaces = have a single D. rxn
• And = plus (+)
HOMEWORK
Pg. 231 #13-22