Balancing Equations

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Balancing Equations
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Balancing Equations
-Chemical equations are just like recipes.
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____ Scoop of ____ Scoop of _____
Slices of ____ PBJ Peanut-
Jelly Bread Sandwiches
butter
N2 H2 ? NH3
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-Chemical equations are just like recipes. They
have ingredients which we called reactants and
a final dish which we call products.
-They also tell you how many of each ingredient
you need and how many servings it makes with big
numbers in front called _____________
coefficients
-To Balance Equations we are going to learn how
to work with the coefficients, since they dont
change the recipe itself. But first a review. . .
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Review
-Matter made up of more than one kind of element
is called a ____________________. -If you
recall compounds have completely unique and often
different Characteristics from the elements
that make them up. -For example C O2 ?
CO2 The reactants in this chemical equation are
__________________ The product in this chemical
equation is _____________________
compound
C, O
2
CO
2
-In this chemical equation we can see that the
reactants, a carbon atom and an oxygen molecule,
combine to form a molecule of the compound
carbon dioxide. However, the properties of just
carbon and oxygen a far different from the
properties of carbon dioxide.
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-Even though the properties of the products may
offer differ from those of the reactants that
formed them, all of the elements that they are
composed of must be accounted for. -For
example C O2 ? CO2 There are
____ carbon atoms There are ____ carbon
atoms in the reactants. in the
products. There are ____ oxygen atoms
There are ____ oxygen atoms in the
reactants. in the products. Amount of
Atoms in Amount of Atoms in Reactants Prod
ucts
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2

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-What is wrong with the following chemical
equation H2 O2 ? H2O
2
H
H
2
O
O
2
1
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-The previous equation is called unbalanced.
It does not follow the law of conservation of
matter because it shows an oxygen atom being
destroyed or lost during the reaction. This is
not possible. All of the atoms in the reactants
must be accounted for in the products.
H2 O2 ? H2O
2
-To fix this chemical equation we are going
balance it. First thing you should note when
you are balancing an equation is that -YOU CAN
NOT ADD OR CHANGE THE SUBSCRIPTS
-H2O is water, but H2O2 is Hydrogen Peroxide.
They are not the same thing! You just changed
the recipe. Thats like saying Peanut- butter
and jelly makes macaroni and cheese! NO NO!
-What you can do is change the amount of the
compounds that already exist by working with the
COEFFICIENTS.
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For example Our earlier example could be
solved by doing the following -This
shows a balanced equation now. The total of
hydrogen atoms in the reactants is _____, which
matches the amount in the product. The total
amount of oxygen atoms in the reactants is
______, which matches the amount in the product.
H2 O2 ? H2O
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2
Start on the smaller side since Coefficients only
bring numbers up.
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H
H
2
4
Coefficients are always only whole numbers. . .
No fractions!
Coefficients can only go infront of the
compounds, not in the middle.
O
O
2
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2
4
2
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-Balance the following equations (Remember you
can only work with the coefficients in the
equation) K Cl2 ? KCl
2
2
1
2
K
K
1
2
Cl
Cl
2
1
2
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N2 O2 ? NO
2
2
N
N
1
2
O
O
2
1
2
10
Na2SO4 CaCl2 ? CaSO4 NaCl
2
1
1
1
Ca
2
2
Ca
Na
Na
Cl
1
2
Cl
2
S
1
S
1
O
4
O
4