1. Stoichiometry From the Greek words “stoicheion” meaning “element”
and “metron” meaning “measure”

2. Stoichiometry
Involves the mass relationships between reactants and products in a chemical reaction.
All reaction stoichiometry relationships start with a balanced chemical equation.
Equation gives the relative numbers of moles of reactants and products.

3. Stoichiometry
Solve problems using RATIOS from the balanced equation.

4. Mole Ratio Ratios produced from the balanced equation 2H2 + O2  2H2O
Possible mole ratios:
2H2 2H2 1O2 1O2 2H2O 2H2
1O2 2H2O 2H2O
2H2O 2H O2

5. Reaction Stoichiometry Problems
Type 1 – given/unknown = mole/mole
Given and unknown quantities are amounts in moles
Amount of given  Amount of unknown
Substance (mol) substance (mol)

6. Reaction Stoichiometry Problems
Type 2 – given/unknown = mole/mass(g)
Given quantity is amount in moles and unknown quantity is amount in grams
Amount of given  Amount of unknown
Substance (mol) substance (grams)

7. Reaction Stoichiometry Problems
Type 3 – given/unknown = mass(g)/mole
Given quantity is in grams, and unknown quantity is amount in moles
Amount of given  Amount of unknown
Substance (grams) substance (mol)

8. Reaction Stoichiometry Problems
Type 4 – given/unknown = mass(g)/mass(g)
Given and unknown quantities are amounts in grams
Amount of given  Amount of unknown
Substance (grams) substance (grams)

9. Reaction Stoichiometry Problems
Solving mole-mole calculations
Write down given quantity in moles
Write mole ratio of unknown/given
Multiply fractions (numerator x numerator; denominator x denominator)
Reduce any remaining fraction to a decimal number

10. Reaction Stoichiometry Problems
Solving mole to mass calculations
Write down given quantity in moles
Multiply by mole ratio of unknown/given
Multiply fractions (numerator x numerator; denominator x denominator)
Reduce any remaining fraction to a decimal number
Multiply by molar mass of unknown.

11. Reaction Stoichiometry Problems
Solving mass to mole calculations
Write down given quantity in grams
Divide by molar mass of given
Multiply by mole ratio of unknown/given
Multiply fractions (numerator x numerator; denominator x denominator)
Reduce any remaining fraction to a decimal number

12. Reaction Stoichiometry Problems
Solving mass-mass calculations
Write down given quantity in grams
Divide by molar mass of given
Multiply by mole ratio of unknown/given
Multiply fractions (numerator x numerator; denominator x denominator)
Reduce any remaining fraction to a decimal number
Multiply by molar mass of unknown

13. Limiting Reagent
Reactant which will LIMIT the amount of product produced.
Need to calculate amount of product for BOTH given reactants to determine which limits the reaction.
The reagent left over is called the excess reactant.

14. Theoretical Yield
Amount of product made under IDEAL conditions. The most possible product you can make. Almost never happens. This is the number you calculate using stoichiometry.

15. Actual Yield
Amount of product made during the actual reaction in the laboratory.

16. Percent Yield Ratio of actual yield/theoretical yield
Tells you how good your reaction really was.
% yield = Actual yield X 100
Theoretical
Yield