1. Stoichiometry
Chapter 3

2. Atomic Masses Based on Carbon-12
Most reliable method: Mass Spectrometry
(pg )
Multiply relative (percent) abundance by the atomic mass for each isotope and then add them together (see pg. 79)

3. The Mole
Avogadro’s Number: x 1023 particles in one mole of a substance
Particles
Atoms (monatomic elements)
Molecules (covalent compounds/diatomic elements)
Formula Units (ionic compounds)
Ions
Use the equality to perform conversions
1 mole = x 1023 particles

4. Molar Mass Find the formula of the compound
List the elements and the number of particles present
Multiply by the atomic mass for each element
Add them all together
Molar Mass (g) = 1 mole

5. Percent Composition Example one: Given Formula
Find Molar Mass; divide each elements individual mass by the total mass of the compound and multiply by 100
Example two: Given mass analysis data
Add masses of all elements together and divide each individual mass by the total mass and multiply by 100

6. Empirical Formula 1 (Simplest ratio of chemical formula)
From Percent Composition Data
Take each element’s percentage and assume it is the grams of that element and change to moles
Divide each # of moles by the smallest # of moles
If they are not all whole numbers, must multiply by a number to get all whole numbers

7. Empirical Formula 2 From mass data given for compound
Change grams to moles for each element
Divide each by the smallest number for the moles
If they are not all whole numbers must multiply by a number to make them all whole numbers
Ex endings:
~.5 x 2; ~.3 or ~.6 x 3; ~.25 or ~.75 x 4

8. Molecular Formulas Need Empirical Formula first
Always given the mass of the Molecular compound.
Find Mass of Empirical formula
Divide Mass of Molecular compound by the mass of Empirical Compound (should be whole #)
Take the Empirical formula and multiply the subscripts by the answer from the division above

9. Chemical Reactions Synthesis: A + B —› AB Decomposition: AB —› A + B
Single Displacement (use reduction potential chart)
Metal Displacement: A + BC —› B + AC
Halogen Displacement: D + EF —› F + ED
Double Replacement: AB + CD —› AD + CB
Use solubility rules to figure out ppt (pg. 144)
Combustion: HC + O2 —› H2O + CO2
HC (Hydrocarbon)

10. Types of Decomposition RXN’s
Elemental
Compound splits into it’s elements
Hydroxide
Metal Hydroxide decomposes into the metal oxide and water
Carbonate
Metal Carbonate decomposes into the metal oxide and carbon dioxide
Chlorate
Metal Chlorate decomposes into the metal chloride and oxygen

11. Stoichiometric Calculations
Must have a balanced equation
Everything hinges on the mole ratio
Whatever you are given convert to moles of that substance
Use the mole ratio
Convert moles of new substance to whatever unit the question asks

12. Limiting Reactant
When given two pieces of data for starting components (reactants) one must perform stoichiometric calculations for both substances to figure out which starting substance produces the least amount of product (it is the reactant that is all used up in the reaction.)

13. Percent Yield Percent Yield = Actual Yield x 100
Theoretical Yield
Are you going crazy yet?