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