1. Stoichiometry

2. What is stoichiometry?
Study of quantitative relationships in balanced chemical equation
Chemical Equations represent chemical reactions

3. Physical vs. Chemical Change
Physical Change =
Chemical Change =
Change in form or appearance
Examples:
Dissolving & phase changes
Change in identity (formula)
Example:
Na(s) + Cl2(g) → NaCl(s)

4. Evidence of a Chemical Reaction
Temperature change
increase or decrease
Emission of Light Energy
Change in identifying property:
- such as color, texture
Formation of a Gas
bubbling, odor
Formation of a Solid
precipitate forms

5. Chemical Equations A + B  C + D
Left Side = Reactants (starting materials)
Right Side = Products (ending materials)
“” is read as “produces or yields”
How show physical state of reactants & products?
(s), (l), (g), (aq)

6. Law of Conservation of Matter
Matter is neither created nor destroyed
in a chemical reaction
Mass reactants = Mass products
Chemical bonds in reactants may break
New bonds may form to produce products
# atoms of each element MUST be same on both sides of equation

7. Coefficients in Chemical Equations
Numbers in front of formulas are called coefficients
apply to everything following in formula
represent numbers of individual atoms, molecules or mole ratios
(Remember the MOLE MAP!)

8. Writing Chemical Equations
Begin with skeleton equation
write correct chemical formulas of reactants and products
Balance the skeleton equation
Use the RAP table

9. Equation Balancing Create a RAP table
table that shows type & # atoms present
Example:
Fe + O2 → Fe2O3
R A P Fe O 1 2 2 3

10. Balance Equation Use coefficients to make sure atoms are =
Update RAP table as go along
Double check your work
Do one last pass to check that all # are same on both sides
Coefficients must be in their lowest possible ratios
Reduce if necessary

11. Example 1 Fe + O2 → Fe2O3 #R atoms #P 1 Fe 2 2 O 3
balance O’s by making 6 on each side
Fe O2 → 2 Fe2O3
O’s are balanced - next balance Fe
4 Fe O2 → 2 Fe2O3
Make one last pass & count all atoms it’s balanced!!

12. Na + H2O → NaOH + H2
#R atoms #P
1 Na 1
2 H
1 O
make # H’s on right even
Na + H2O → 2 NaOH + H2
balance Na’s by adding 2
2 Na + H2O → 2 NaOH + H2
One last pass: need to balance O and H on left
2 Na H2O → 2 NaOH + H2

13. 2 AgNO3 + MgCl2  Mg(NO3)2 + AgCl
Hint: can treat polyatomic [NO3-1] as one atom
#R atom #P
1 Ag 1
1 NO3 2
1 Mg 1
2 Cl 1
Balance NO3-1 on the left with a 2
2 AgNO3 + MgCl2  Mg(NO3)2 + AgCl
Balance Ag’s and Cl with a 2
2 AgNO3 + MgCl2  Mg(NO3) AgCl
Make on last pass to count all atoms