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Today we are going to learn how
to balance chemical equation!
Why do chemical equations need
to be balanced?
Because…in a chemical equations, the mass of the
______________________ must equal the mass of
the _____________________
This is called the
______________________________________
______________________: takes place
when new products are made from
reactants
Possible signs of a chemical reaction:
________________________________
________________________________
________________________________
Definitions:
Reactants – _______________________
Products – ________________________
______________________– Describes what
happens in a chemical reaction, it identifies
_______________________________,
________________________, formulas of
the participants, phases of the participants
(solid, liquid, or gas) and ________________
of each substance
States of matter that can be included
in the chemical equation:
(g) = __________________
(s) = ___________________
(l) = ____________________
(aq) = _____________________
Other important information:
single arrow (→) = __________________,
shows the direction of action
delta ( Δ ) = shows that
__________________________________
double arrow ( ↔ ) = shows that the
reaction is
__________________________________
__________________________________
Mini Math Lesson:
Distributive Property
2(3y + 4) = ________
2 x 3 = _____ 2 x 4 = _____
You are distributing the “2”
The “2” in this case is called the “____________”
Mini Math Lesson: Distributive Property
3(4z + 6) =
_______________
10(5v + 3) =
_______________
In balancing chemical equations, it works the
same way…
Learning how to count atoms!
Let’s use the equations for water:
H2 + O  H2O
Equation is
given to you:
This part
you have
to write
under the
equation:
H2 + 01  H201
_____ H
_____ O
(reactants)
_____ H
_____ O
(products)
Imaginary!
Learning how to count atoms
Equation is with coefficients!
given to you:
2 H2 + 2 01  2 H201
This part
you have to
write under
the
equation:
_____ H
(2 x 2) =
_____ H
Imaginary!
(2 x 2) =
_____ O
_____ O
(2 x 1) =
(2 x 1) =
(__________) (__________)
Balanced chemical equations:
H2 + 0  H20
____ H
____ O
(reactants)
These are
_____________:
numbers
that come
before the
molecule
and need to be
distributed
to the whole
molecule
These are
____ H ____________
____ O ___________:
they tell you
(products) how many of
2 H 2 + 2 0  2 H 20
____ H
____ O
(reactants)
each atom
there are
It is still
____ H
balanced,
____ O even though
(products) I’ve added
coefficients!
Steps to balancing a chemical equation:
Step 1 – Count _________________________
in the unbalanced chemical equation
Step 2 – Add one ________________________
Step 3 – Add a second ____________________
______________________________________
Step 4 – Continue to add __________________
______________________________________
______________________________________
______________________________________
Let’s try an example together!
Step 1: Count the atoms
SnO2 + H2  Sn + H20
______ Sn
_____ Sn
______ H
______ H
______ O
_____ O
(reactants)
(products)
Uh ohhhhhhhh! The oxygens aren’t
balanced!
SnO2 + H2  Sn + H20
_____ Sn
_____ H
_____ O
(reactants)
_____ Sn
_____ H
_____ O
(products)
• Since this is the original equation, we cannot
__________________ the number of oxygens so that
both will be “1”.
• Instead, our only option is to ____________________
the number of oxygens.
• For example, both sides can be increased to “2” each,
or “4” each, etc…
What do we do?! We have to balance the
equation! Step 2: ADD COEFFICIENTS!
We need “2 O” on the reactants side (left)
and “2 O” on the products side (right)
___ SnO2 + ___ H2  ___ Sn + ___ H20
______ Sn
______ H
______ O
(reactants)
______ Sn
______ H
______ O
(products)
But it’s still not balanced, but we are 1 step closer!
It’s like a puzzle!
Tip 1: Only add 1 _________________
at a time. It is much easier this way!
Tip 2: Always start by _____________
a coefficient to the more
________________ molecule. For
example, chose H2O over O2. It will be
easier to change O2 at the last minute,
but it will be much harder if you wait
till the end to manipulate H2O.
Step 3: ADD ANOTHER COEFFICIENT!
Now we need “4 H” on the reactants side (left)
and “4 H” on the products side (right)
___ SnO2 + ___ H2  ___ Sn + ___ H20
_____ Sn
_____ H
_____ O
(reactants)
_____ Sn
_____ H
_____ O
(products)
We’ve done it! The equation is balanced!
Let’s try another example together!
Step 1: Count the atoms
CH4 + O2  CO2 + H20
_____ C
_____ H
_____ O
(reactants)
_____ C
_____ H
_____ O
(products)
Uh ohhhhhhhh! The hydrogens AND the
oxygens aren’t balanced!
Step 2: Add coefficients
Tip 2: It’s always a good idea to leave the single element, in
this case O2 till last because it will be the easiest to change.
___ CH4 + ___ O2  ___ CO2 + ___ H20
_____ C
_____ H
_____ O
(reactants)
_____ C
_____ H
_____ O
(products)
Now only the oxygens aren’t balanced!
Step 3: Add a second coefficient
Ask yourself: “How can I get 4 oxygens on the reactants
side?”
___ CH4 + ___ O2  ___ CO2 + ___ H20
____ C
____ H
____ O
(reactants)
____ C
____ H
____ O
(products)
Now we’ve balanced the chemical
equation!
One more!
Step 1: Count the atoms
SiO2 + HF  SiF4 + H20
____ Si
____ H
____ O
____ F
(reactants)
____ Si
____ H
____ O
____ F
(products)
Uh ohhhhhhhh! The hydrogens AND the
fluorines aren’t balanced!
Step 2: Add a coefficient!
What atom is going to see the biggest increase?
d
___ SiO2 + ___ HF  ___ SiF4 + ___ H20
____ Si
____ H
____ O
____ F
(reactants)
____ Si
____ H
____ O
____ F
(products)
Now the fluorines are balanced!
But we still have an unequal amount of oxygens!
Step 3: Add another coefficient!
Ask yourself: How can I get 4 oxygens on the products
side?
___ SiO2 + ___ HF  ___ SiF4 + ___ H20
____ Si
____ H
____ O
____ F
(reactants)
____ Si
____ H
____ O
____ F
(products)
Now the equation is completely balanced!