Balancing
Chemical Reactions
Also Known As…
How to become the
baddest, craziest
chemical assassin
to walk the planet!
Types of Chemical Equations
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There are a few different ways to describe any chemical
reaction.
Let’s look at the chemical reaction that describes the
decomposition (breaking apart) of water.
Word Equations – These equations use the names of the
substances involved in the “reactants  products” format.
Water  Oxygen gas + Hydrogen gas
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Skeleton Equations – These use the chemical formulas of
the substances in the “reactants  products” format.
H2O  O2 + H2
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A closer look at the skeleton equation will reveal a
problem…We have only one oxygen atom going into the
reaction, but, there are two oxygen atoms coming out of the
reaction.
The Law of Conservation of Mass
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The Law of Conservation of Mass states that
the mass of the atoms making up the reactants
will be the same as the mass of the atoms
making up the products.
Atoms can’t be created or destroyed so this law
basically means…
“What goes in…must come out!”
For instance, if a chemical reaction has five
carbon atoms going in with the reactants – it
must have five carbon atoms exiting the reaction
as part of the products.
For this reason, we must “balance” all of our
chemical equations, because, what goes in…must
come out!
Balancing Act
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To balance a chemical equation – you first need a word
equation. Once you have that you can figure out the proper
formulas of the substances involved.
A skeleton equation shows a chemical reaction by using just
the formulas of the reactants and products. A yield arrow ()
is also used to show the direction of the reaction.
Now balance the skeleton equation by counting atoms and
placing the appropriate coefficients in front of the formulas
that need adjusting.
Coefficients are the large numbers in front of a chemical
formula – you can adjust these. The smaller numbers within
the formula are subscripts – if you touch these, I know places
they will never find your body!
If both sides have the same number and type of atoms, you
have achieved the pinnacle of chemistry expressionism! You
now have a balanced chemical equation.
All work in chemistry usually begins with a chemical equation
that has the proper formulas and is balanced properly.
How To Pass Grade 10 Chemistry
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Did you use the
proper formulas
based on the word
equation provided.
Did you add only
coefficients? I will
snap if you use
subscripts!
Did you go back
and double check
your balancing act?
Practice Equations
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1.
2.
3.
4.
5.
6.
7.
8.
Try to balance the following chemical equations.
Remember, count one element at a time and think – what
goes in, must come out!...or else!
+
3 MgCl2
+
2 AlBr3
CH4
+
+
2 NaOH
H 2O
+
Mg(NO3)2 +
+
2 AlPO4
C3H 8
+
2 FeBr3  3 MgBr2 + 2 FeCl3

3 F2
2 AlF3 +
3 Br2

+
CO2
2 O2
2 H2O
H2SO4 
Na2SO4 + 2 H2O
CO2

H2CO3
(already balanced)
Mg(OH)2 + 2 NaNO3
2 NaOH 
3 Mg(ClO3)2  2 Al(ClO3)3 + Mg3(PO4)2

+
5 O2
3 CO2
4 H 2O
One Last Reminder!
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You only add coefficients – the big numbers in front. I will
completely lose it if you start throwing around those little
subscripts like you are some sort of chemistry revolutionary!
THE END