Transcript H2 + O2 => H2O

Balancing Equations
Before we start, there are some
things we all need to know
H2O means there are 2
Hydrogen and 1 Oxygen atoms
in this compound.

The subscript number AFTER a symbol
tells us how many of that atom is in the
molecule. (or compound)
2H2O means H2O and H2O
Totaling 4 Hydrogen and 2
Oxygen atoms.

The number in FRONT of the molecule is called the
coefficient.
We can add molecules to the
equation, but not single atoms.

We can ONLY change the Coefficient of
the molecule, NEVER the subscript.
Remembering the Law of
Conservation of Mass:
The law of conservation of mass states
that mass is neither created nor destroyed
in a chemical reaction.
 Meaning that during a chemical reaction,
matter is not created, nor is it destroyed. It
is however rearranged.
 (This is huge in chemistry, be sure you
know this…..KNOW IT)

Ok Here we go

On a sheet of paper, let’s work some
equations together
Lets start by burning gas methane
(CH4)

We know that this reaction consumes oxygen
This produces water and carbon dioxide
 Below is an unbalanced chemical equation.

Start by counting the atoms in the
reactants and products.
 The
carbons are happy and even,
so are the hydrogens, but the
oxygens are not balanced

Sure the easy way of solving this would be to
change the O2 to O4, but that is changing the
molecule, and thus cheating. Don’t cheat, just
add another O2 molecule and life is good and all
is happy.

Note that only the number of molecules
has been balanced, and no molecules
have been changed.
REMEMBER
You can change the number of the
molecules, but NEVER change just the
number of atoms. (it changes the
molecule)
 Remember, it is like using Legos

Any questions before we move on?
On a separate sheet of paper
write down the following
equations, and then balance it

Good luck.
H 2 + O2
H 2O
2
2H2O
H2 + O2
Na + O2 => Na2O2
2Na + O2 => Na2O2
C + S8 => CS2
4C
+ S8 => 4CS2
C + O2 => CO2
C
+ O2 => CO2
Na + NaNO3 => Na2O + N2
 10Na
+ 2NaNO3 => 6Na2O + N2
N2 + O2 => N2O5
2N2
+ 5O2 => 2N2O5
K + B2O3 => K2O + B
6K
+ B2O3 => 3K2O + 2B
HCl + NaOH => NaCl + H2O
 HCl
+ NaOH => NaCl + H2O
FeS2 + O2 => Fe2O3 + SO2
 4FeS2
+ 11O2 => 2Fe2O3 + 8SO2
H3PO4 + KOH => K3PO4 + H2O
 H3PO4
+ 3KOH => K3PO4 + 3H2O
Brain going Squishie Squishie yet?

Great  Lets start our practice sheet 