1. 11.2 Stoichiometric Calculations Discovery School Ashley Lardizabal
Ch 11 Stoichiometry
11.2 Stoichiometric Calculations
Discovery School
Ashley Lardizabal

2. OBJECTIVES
Explain the sequence of steps used in solving stoichiometric problems.
Use the steps to solve stoichiometric problems

3. Stoichiometric Calculations
Need to obtain a certain amount of product from a reaction.
Need to know how much product will be formed if a certain amount of reactant is used.

4. Using Stoichiometry
STOICHIOMETRY is the study of quantitative relationships between the amounts of reactants used and the amount of products formed by the chemical reaction.
Begin with a balanced chemical equation
Mole ratio are also needed
Finally, mass to mole conversions

5. Stoichiometric mole-to-mole conversions
2K(s) + 2H2O  2KOH(aq) + H2(g)
Vigorous reaction between potassium and water

6. Stoichiometric mole-to-mole conversions
2K(s) + 2H2O  2KOH(aq) + H2(g)
How can you determine the number of moles of hydrogen produced when mole of pottasium is used?
Balanced chemical equation
Identify known and unknown
Mole to mole conversions

7. Stoichiometric mole-to-mole conversions
2K(s) + 2H2O  2KOH(aq) + H2(g)
KNOWN: mol K
UNKNOWN: moles of
Both in moles so mole-to-mole conversion
MOLE RATIO:
Moles of known x moles of unknown = moles of unknown
moles of known

8. Stoichiometric mole-to-mole conversions
2K(s) + 2H2O  2KOH(aq) + H2(g)
0.040 mol K x 1 mol H2 = mol H2
2 mol K
If you put mol K into water, mol of H2 will be produced.

9. Example: Stoichiometric Mole-to-Mole Conversion
One disadvantage of burning propane (C3H8) is that carbon dioxide (CO2) is one of the products. The released carbon dioxide increases the growing concentration of CO2 in the atmosphere. How many mole of carbon dioxide are produced when 10.0 moles of propane are burned in excess oxygen in a gas grill?

10. Stoichiometric mole-to-mass conversions
You know the number of moles of reactant and produced in a reaction and you want to calculate the mass of another product or reactant.
This is an example of mole-to-mass conversion
mol known x mol unknown x molar mass unknown = g of unknown
mol known mol of known

11. EXAMPLE: Stoichiometric Mole to Mass Conversion
Determine the mass of sodium chloride or table salt (NaCl) produced when 1.25 moles of chlorine gas reacts vigorously with sodium.

12. Stoichiometric Mass-to-Mass Conversions
If you want to carry out a chemical reaction in your laboratory, you need to know how much of each reactant to use in order to produce the mass of product you require.

13. Example: Stoichiometric Mass-to-Mass Conversion
Ammonium nitrate (NH4NO3), an important fertilizer, produce N2O gas and H2O when it decomposes. Determine the mass of water produced from the decomposition of 2.5 g of solid ammonium nitrate.

14. Steps in Stoichiometric Calculations
Write a balanced equation.
Determine the moles of the given substance using a mass-to-mass conversion.
Determine the moles of the unknown substance from the moles of the given substance

15. HOMEWORK:
Assessment and Practice Problems # 9-19