STARTER

• Try to name the following compounds

• You have 5 minutes!

H NO3 Zn Cl2

H2 SO4 Cu Cl2

Ca (OH)2 Ca CO3

Ag Br Na OH

Ag2 O Ca SO4

Cu O Mg O

Ag NO3H Cl

Na2 SO4Na Cl

Balancing Equations

Everyone should:Be able to balance simple equations

Most people will:Balance equations using compounds like OH- NO3 -

SO4 2-

Some people will:Be able to balance equations with unusual compounds

The law of conservation of matter

• ATOMS CANNOT BE CREATED OR DESTROYED!

The idea of the famous scientist John Dalton in 1700's.

Hydrogen + chlorine hydrogen chloride

H2 + Cl2 HCl

Remember: Hydrogen and Chlorine are diatomic

+

REACTANTS

2 H atoms2 Cl atoms

PRODUCTS

1 H atom1 Cl atom

This is impossible as it implies that atoms have been destroyed.

What do we do?

We need to make the number of atoms equal on both sides of the equation, in order to get the equation to BALANCE.

Equation is now balanced, as there are the same number hydrogen atoms (2) and the same number of chlorine atoms (2) on the products and reactant side.

Firstly you need an equation with the correct “formulae” You’ll probably be given this in the question

Just like this one

Mg + O2 MgO

Then all you do is list the atoms that are involved on each side of the arrow

Mg + O2 MgO

Mg Mg O O

[1] Just count up the atoms on each side

Then start balancing:

Mg + O2 MgO

2

The numbers aren’t balanced, so make your adjustments:

And adjust totals

Mg + O2 MgO2

Mg 1 Mg 1 O 2 O

Mg 1 Mg 2 O 2 O 2

Mg + O2 MgO2

But the numbers still aren’t equal

2

And adjust totals again

NOW BOTH SIDES HAVE EQUAL NUMBERS OF ATOMS

WE SAY THAT THE EQUATION IS BALANCED!!

2

GROUP ACTIVITY: Try to balance these equations

You have 5 minutes!

[1] Na + Cl2 NaCl

[2] CH4 + O2 CO2 + H2O

[4] Al + O2 Al2O3

[3] Li + HNO3 LiNO3 + H2

Why didn’t anyone tell me it was so easy

to balance equations???!!!

How did you get on??

[1] 2 Na + Cl2 2 NaCl

[2] CH4 + 2 O2 CO2 + 2 H2O

[4] 4 Al + 3 O2 2 Al2O3

[3] 2 Li + 2 HNO3 2 LiNO3 + H2

Here are the answers:

ExamplesIt’s best to balance using whole numbers

22

3 22

24

22