StoichiometryMrs. Page

Chem. 10

2014-2015

What is Stoichiometry?

• The study of chemistry that looks at the relationship between the mass of the reactants and products in a chemical reaction.

• Uses chemical equations and mole calculations to look at the relationship between reactants and products.

How does this relate to my life?

Chewy Peanut Butter Chocolate Chip CookiesRecipe for 24 cookies½ cup butter½ cup peanut butter1 cup brown sugar½ cup white sugar2 eggs2 TBSP corn syrup2 TBSP water2 tsp vanilla2 ½ cups flour1 tsp baking soda½ tsp salt2 cup choc. Chips

http://allrecipes.com/Recipe/Chewy-Peanut-Butter-Chocolate-Chip-Cookies/Detail.aspx?evt19=1&referringHubId=362

You want to make as many cookies as possible but you only have 7 eggs. How many cookies can you make?

∙24 𝑐𝑜𝑜𝑘𝑖𝑒𝑠2𝑒𝑔𝑔𝑠

7𝑒𝑔𝑔𝑠 ¿84 𝑐𝑜𝑜𝑘𝑖𝑒𝑠

Mole Ratios

2 Mg(s) + O2 (g) 2 MgO(s)

• The coefficients of a BALANCED chemical equation tell us the MOLE RATIO of the reactants and the products

• In this reaction: 2 moles of magnesium metal react with 1 mole of oxygen gas to produce 2 moles of magnesium oxide

Tell the mole ratios for the following reactions

• 2KClO3 2KCl + 3O2

• Cu + 2AgNO3 2Ag + Cu(NO3)2

• 4NH3 + 5O2 6H2O + 4NO

• C4H10 + O2 CO2 + H2O (CAREFUL!)

Steps to Solving Stoichiometry Problems

1. Write a balanced equation.

2. Identify known & unknown.

3. Line up conversion factors• Mole ratios mole mole (from balanced equation)

• Molar mass (Mr) mole grams (periodic table)

• Avogadro mole molecules/atoms/f. units

4. Check you solution

How many moles of KClO3(aq) must decompose in order to produce 9 moles of oxygen gas?

KClO3(aq) KCl(aq) + O2(g)2

• Balance the Equation

3

• Start with what you know9 mol O2

• Set up conversions 3 mol O2

2 mol KClO3

• Calculate & Check

6 mol KClO3

2

Mass Stoichiometry

How many grams of silver will be formed from 12.0 g copper?

Cu + AgNO3 Ag + Cu(NO3)22• Balance the Equation

2

• Start with what you know12.0 g Cu• Set up conversions 63.546 g Cu

1 mol Cu1 mol Cu2 mol Ag

1 mol Ag

107.868 g Ag

• Calculate & Check

40.7 g Ag

Given: NH3 + O2 H2O + NOa) How many moles of H2O can be made using 0.5 mol NH3?

NH3 + O2 H2O + NO4

• Balance the Equation

6

• Start with what you know0.5 mol NH3

• Set up conversions 4 mol NH3

6 mol H2O

• Calculate & Check

0.8 mol H2O

45

4NH3 + 5O2 6H2O + 4NOb) what mass of NH3 is needed to make 1.5 mol NO?

• Balance the Equation

• Start with what you know

1.5 mol NO• Set up conversions

4 mol NO

4 mol NH3

1 mol NH3

17.031 g NH3• Calculate & Check

26 g NH3

Given: 4NH3 + 5O2 6H2O + 4NOc) how many grams of NO can be made from 120.0 g of O2?

• Balance the Equation

• Start with what you know

120.0 g O2• Set up conversions

31.998 g O2

1 mol O2

5 mol O2

4 mol NO

1 mol NO

30.006 g NO• Calculate & Check

90.02 g NO

Your TurnFollow the rules for significant digits. Show all calculations.

1. C4H10 + O2 CO2 + H2O

a) what mass of O2 will react with 400.0 g C4H10?

b) how many moles of water are formed in a)?

2. HCl + Al(OH)3 H2O + AlCl3

How many grams of aluminum hydroxide will react with 5.3 moles of HCl?

3. Ca(ClO3)2 CaCl2 + O2

What mass of O2 results from the decomposition of 1.00 kg of calcium chlorate?

4. The reaction of Ca with water can be predicted using the activity series. What mass of water is needed to completely react with 2.35 g of Ca?

More Practice ProblemsFollow the rules for significant digits. Show all calculations.

5. Fe2O3 + CO Fe + CO2.

a) How many moles of carbon monoxide are required to react with 163.0 g of iron(III) oxide?

b) How many grams of CO2 are produced from a reaction that also produces 23.9 grams of Fe?

6. Cu + HNO3 Cu(NO3)2 + H2O + NO

c) how many moles of copper(II) nitrate can be prepared from 17.0 moles of Cu?

d) how many grams of copper(II) nitrate can be prepared using 3.8 moles of HNO3?

e) what mass of water results from the reaction of 8.50 kg of copper metal?