Chapter 12- Stoichiometry

BBAA MassMoleMoleMass

• Stoichiometry- using chemical formulas to determine molar and mass relationships from balanced chemical equations

The Mole Ratio

• PRACTICE

OHOH 222 22

Mole Ratio Practice

Write all the possible mole relationships that can be written from the following equation.

332332 __)(__)(__)(__ MgCOOHAlOHMgCOAl

Mole:Mole

__CO2(g) + __LiOH(s) __Li2CO3(s) + __H2O(l)

1.How many moles of lithium hydroxide are required to react with 20 moles of CO2? (answer: 40 moles lithium hydroxide)

2.If 1.25 moles of water are produced, how many moles of carbon dioxide were used?

3.You have 3.55 moles of CO2, how moles of lithium carbonate can you make?

Mole:Mass

• CO2(g) + H2O(l) C6H12O6(s) + O2(g)

1.What mass of CO2, in grams, is needed to react with 3.00 moles of H2O during photosynthesis? (Answer: 132 g)

2.How many grams of glucose can be made from those 3.00 moles of water?

3. It is measured that 11.63 grams of oxygen are produced, how many moles of carbon dioxide must have been used?

Mass:Mass:

Sn(s) + HF(g) SnF2(s) + H2(g)

1.How many grams of SnF2 can be produced from

30.0 g of tin? (answer: 39.6 g)

2. If 2.54g of hydrogen are produced, how many grams of tin were used?

3. If you have 55.63 g of tin available, what is the maximum amount of SnF2 you can make?

Practice(try these tonight)

1. Sulfuric acid reacts with sodium hydroxide in a double replacement reaction. If you start with 5.25 moles of NaOH, how many moles of water can you make?

2. If you start with 11.34 grams of NaOH, how many moles of sodium sulfate can you make?

3. If you start with 55.1 grams of NaOH, how many grams of sodium sulfate can you produce?

Limiting Reactants

Ingredients2 1/4 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 1 cup (2 sticks) butter, softened 3/4 cup granulated sugar 3/4 cup packed brown sugar 1 teaspoon vanilla extract 2 large eggs 2 cups (12-oz. pkg.) 1 cup chopped nuts

Yield: 24 cookies

How many cookies can be made if I only have 1 stick of butter and 1 cup of sugar (and the exact quantity of the other ingredients in the recipe)?

Limiting Reactants (5 steps) Strategy #1

1. Write and/or balance the equation

___Mg3N2 + ___H2O ___Mg(OH)2 + __NH3

2. Determine the mole ratio of the reactants in the equation

3. Determine the mole ratio of the reactants from the given quantities in the problem (Hint: Convert grams to moles)

4. Compare the mole ratios to determine which reactant is limiting.

5. Using the limiting reactant, determine the amount of product that can be produced using stoichiometry.

Limiting Reactants (3 steps) Strategy #2

___KBr(aq) + ___Cl2(aq) ___KCl(aq) + ___Br2(l)

• Write and/or balance the equation.

• Using Stoichiometry, solve for the amount of product that can be produced from one of the reactants.

• Using Stoichiometry, solve for the amount of product that can be produced from the other reactant.

Whichever reactant yields the least amount of product is the limiting reactant.

Handling Excess Reactant

If one reactant is limiting, then the other is in excess

To determine how much of the excess reactant remains after the reaction is complete, You need to determine how much of it is actually needed through stoichiometry using the limiting reactant as a starting point. Then, subtract this quantity from the amount given in the equation.

Percent Yield(How good of a scientist are you…..Maybe?)

___Al(OH)3 (s)   +  ___HCl (aq)  g  ___AlCl3 (aq)   +  ___ H2O (l)

1. If you start with 50.3 g of Al(OH)3 and an excel of HCl and you isolate 39.5 g of AlCl3, what is the percent yield?

ldPercentYiexlTheoretica

Actual100 (amount produced in the lab)

(amount determined through stoichiometry)