1. And the Law of Conservation of Mass
8.5F Balancing Equations
And the Law of Conservation of Mass

2. Main Idea
8.5F - Recognize whether a chemical equation containing coefficients is balanced or not and how that relates to the law of conservation of mass.

3. Notes
A chemical equation joins two separate chemical formulas together. 2H2 + O2  2H2O
The whole thing is a chemical equation
2H2 + O2  2H2O
Chemical Formulas

4. Notes Rats Eat Poop = reactants, equals, products 2H2 + O2  2H2O
To keep from blowing up the world we have to make sure that all equations are balanced.
When they are unbalanced you have a chemical reaction
This is why we learned to count atoms

5. Notes
The Law of Conservation of Mass – Mass can neither be c nor it can just change forms.
You have to know this term forever and ever now.
States that what is the reactant side of the equation has to be on the product side (so you don’t blow up the world)
Very similar to the Law of Conservation of Energy
created
destroyed,

6. Notes
To balance an equation you have to count the atoms on the reactant side and the product side.
2H2 + O2  2H2O
H= H=
O= O=
Is this equation balanced? 4 4 2 2
YES

7. Notes
How to balance an equation:
Count the atoms on both sides
H2 + O2  2H2O
H= H=
O= O=
So what now?
What can we add to make them even? (what number could you multiply the atoms by to even out the numbers?)
WARNING!!! You can only change the Co- effiecient. NEVER the subscript. 2 4 2 2

8. Notes
It will take you a little bit of trail and error to figure it out. It takes patience.
Practice one:
_____ Fe + _____ AgNO3 → _____ Fe(NO3)2 + _____ Ag
Fe= Fe=
Ag= Ag=
N= N=
O= O=

9. Brain Break

10. Notes Practice: ____ Na3PO4 + ____ KOH  ____ NaOH + ____ K3PO4
____ P4 + ____ O2  ____ P2O3
____ CF4 + ____ Br2  ____ CBr4 + ____ F2
____ Al + ____ HCl  ____ H2 + ____ AlCl3