1. #45 Balancing equations notes

2. Count the atoms
4 Al(OH)3
3(NH3)3(PO4)2

3. Chemical Equation Vocab
2H O2  2H2O
Coefficient – a # that is in front of the element or compound and distributed to ALL associated elements or compounds
Subscript – identifies the amount of atoms in an element
Reactant(s) – the starting material in a chemical reaction (on the left)
Product(s) – the substance formed from the chemical reactants ( on the right)
Yield – like a equal sign; separates the products from the reactants

4. *Law of conservation of mass/matter
The Law of Conservation of Mass/Matter states that matter cannot be created or destroyed
Meaning, the number of atoms each element has MUST be equal on both sides of the chemical equation
A way to remember this is:
What goes in must come out

5. Chemical equations MUST be balanced!
Why?
Because the Law of Conservation of Mass or Matter

6. So how do I balance equations?
*In balancing equations, you CANNOT change the subscripts!
If you change the subscript, you change the substance
For example:
H H2O2

7. *So how do you make #’s work if you cannot change subscripts?
You change the COEFFICIENTS and recount the atoms

8. 2 h2O = H2O + H2O
How do you count the atoms on the reactant side (left side)?
How about the product side (right side)?

9. *Rules for balancing equations (be prepared to use your eraser)
Draw an line underneath the yield sign of the equation. Count ALL atoms on both sides of the equation.
Pick an element that is not equal on both sides and find the least common multiple.
Add coefficient to the chosen element and recount atoms
Repeat steps 2 and 3 for unbalanced elements and recount atoms. (Until all elements are even)
Write the balanced equation
Al O2  Al2O2
Is it balanced?

10. Let’s try these two together
Na Cl2  NaCl
Mg N2  Mg3N2

11. You try
Cr O2  Cr2O3
NH O2  N H2O