Balancing Equations
Mar 26, 2015
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.
H2 + O2 H2O
2 H2 + O2 2H2O
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