Download 9. Balancing Equations

AND
Types of Reactions
Let the fun begin!
Why do we need to balance equations?
To satisfy the Law of Conservation of Mass
Which says:
Matter cannot be created or destroyed;
therefore,
You must have the same number of atoms on
each side of a chemical equation to show
conservation of mass.
ie. Reactants = Products
Step 1
• Make sure compounds are balanced;
In this reaction, the reactant compounds’
charges are not balanced:
Na+1O-2 + Ba+2Cl-1 --- Na+1Cl-1 + Ba+2O-2
Use subscripts to balance the compounds
to zero:
Na2O + BaCl2 - NaCl + BaO
(+2)+(-2) = 0
( +2)(-2) = 0
Step 2
• Use coefficients to balance the numbers of
atoms on each side;
Na2O + BaCl2 - NaCl + BaO
How many sodiums on the left? 2; how
many on the right/ 1; put a coefficient 2 in
front of the one on the right. How many
oxygens on the left/ on the right/, etc.
Na2O + BaCl2 - 2NaCl + BaO
Step 3:
Check to Insure the same number of
atoms on both sides
Na2O + BaCl2 - 2NaCl + BaO
•
•
•
•
•
Atom
Na
O
Ba
Cl
Left
2
1
1
2
Right
2
1
1
2
• Balanced! Mother Nature would be proud!
• Great job!
Let’s Practice!
Balance this equation:
Al + CuCl2 --- AlCl3 + Cu
How many aluminum atoms on the left? On
the right?
How many copper atoms on the left? On the
right?
How many chlorine atoms on the left? On the
right?
Use coefficients to balance each atom!
Answer:
2Al + 3CuCl2 --- 2AlCl3 + 3Cu
Balance this equation:
Na3PO4 + CuSO4 - Na2SO4 + Cu3(PO4)2
Answer:
Na3PO4 + CuSO4 - Na2SO4 + Cu3(PO4)2
First ask, “how many sodiums on the left, how many sodiums
on the right?” Use coefficients to balance each of the atoms
left to right.
2Na3PO4 + 3CuSO4 -- 3Na2SO4 + Cu3(PO4)2
Balance this equation:
C4H10 + O2 --- CO2 + H2O + E
Answer:
C4H10 + 6.5O2 --- 4CO2 + 5H2O + E
What does it really look like
on a molecular level?
N2
+
H2 --- NH3
The molecules would look
like this:
N2
+ H2  NH3
If the equation is balanced?
You need to show the same number of
atoms on each side of the arrow:
• N2 + 3H2  2 NH3
Practice More!
• Try this helpful link:
• http://newtraditions.chem.wisc.edu/FPT
S/fbeqns/chemeqnf.htm
Types of Reactions
Why? They help you predict products.
Synthesis (direct combination)
Decomposition
Single Replacement
Double Replacement
Combustion
Acid Base Neutralization
Synthesis (direct
combination)
A + B  AB
Decomposition
AB  A + B
Single Replacement
ABaq + Cs  CBaq + As
Double Replacement
ABaq + CDaq  CBs + ADaq
Combustion
CxHx + O2  CO2 + H2O + E
(hydrocarbon)
Acid Base Neutralization
Acid + Base  Salt + Water
HA + BOH  BA + H2O
Balancing Equations:
or
Definitely HOT!
The End
… of this slide show, but just the beginning
of more chemistry!