BRN

Complete the table using the balanced chemical reaction:

______CH4 + ______O2 _____CO2 + _____H2O

Molecules CH4

Molecules O2

→Molecules

CO2

Molecules H2O

4.0 →

→ 5.0

Stoichiometry Notes

New Section in Table of Contents

Real Life Application

Ingredients

2 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.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels

1 cup chopped nuts

Real Life Application

We cannot forget about the law of conservation of mass.

The mass of what we put in must be equal to what we get out.

KC 1: The excess reactants are all the leftover unused reactants. (The reactant that’s leftover).

Particle and Mole Relationships

Chemical reactions stop when one of the reactants is used up

KC 2: Stoichiometry is the study of quantitative relationships between the amounts of reactants used and amounts of products formed by a chemical reaction

So based on how much reactant you put in you can calculate how much product you will get out

Particle and Mole Relationships

Particle and Mole Relationships

KC 3: A mole ratio is a ratio between the numbers of moles of any 2 substances in a balanced equation

This can only be determined from a balanced chemical equation

Particle and Mole Relationships

Let practice: What is the mole-to-mole ratio for… 10C2H4O + 15O2 20CO2 + 2H2O

CH4 + 2O2 CO2 + 2H2O

H2 + O2 H2O

Using Stoichiometry

CH4 + 2O2 CO2 + 2H2O

Mol CH4 Mole H2O

Using Stoichiometry

Key Concept 4:

How many moles of SO3 are formed if you start with 5.25 moles of Sulfur and have excess Oxygen?

____S + ____O2 ____SO3

Using Stoichiometry

Key Concept 5:

How many moles of SO3 are formed if you start with 0.25 moles of oxygen and have excess sulfur?

____S + ____O2 ____SO3

Using Stoichiometry

Key Concept 6:

How many moles of water are formed if you start with 0.345 moles of CH4?

______CH4 + ______O2 → _____CO2 + _____H2O

Lab Introduction

Make your own soda!

Using Stoichiometry How many grams of Fe2O3 are formed when 12.37g

of iron reacts with excess oxygen using the balanced chemical equation below:

4Fe(s) + 3O2(g) 2Fe2O3(s)

Using Stoichiometry

4Fe(s) + 3O2(g) 2Fe2O3(s)

12.37g Fe

Mol Fe Mole Fe2O3

?? g Fe2O3

Using StoichiometryKey Concept 7:

How many grams of lithium nitrate will be needed to make 250.0 grams of lithium sulfate, assuming that you have an adequate amount of lead (IV) sulfate to do the reaction?

____Pb(SO4)2 + ____LiNO3 ____Pb(NO3)4 + ____Li2SO4

Using StoichiometryKey Concept 8:

How many grams of sodium sulfate will be formed if you start with 20.0 grams of sodium hydroxide and you have an excess of sulfuric acid?

____NaOH + ____H2SO4 ____H2O + ____Na2SO4

Using StoichiometryKey Concept 9:

How many grams of water will be formed if you start with 200.0 grams of sodium hydroxide and you have an excess of sulfuric acid?

____NaOH + ____H2SO4 ____H2O + ____Na2SO4

Practice

How many grams of CaCl2 are formed when 21.3g of Ca(OH)2 reacts with excess HCl?

_____Ca(OH)2 + _____HCl ______CaCl2 + ______H2O

Practice How many grams of BaCl2 are formed from

6.0 moles of Ba(ClO3)2?

_______Ba(ClO3)2 → _______BaCl2 + _____O2

Practice Iron(III) oxide, Fe2O3, can be reduced to iron by

passing carbon monoxide, CO, over the heated oxide. How many moles of iron can be produced from 1.234 moles of Fe2O3 oxide and excess carbon monoxide?

______Fe2O3(s) + _____CO(g) _____Fe(s) + _____CO2(g)

Practice Butyne, C4H6, burns in the presence of oxygen in air

to produce carbon dioxide, CO2, and water H2O. How many moles of oxygen will be required to produce 45.99 moles of carbon dioxide?

______C4H6 + ______O2 ______CO2 + ______H2O

Practice The following reaction can be used to remove CO2

breathed out by astronauts in a spacecraft.

2 LiOH + 1 CO2 → 1 Li2CO3 + 1 H2O

a. How many grams of carbon dioxide can be removed by 5.5mol LiOH?

b. How many grams of water could be produced from 2.23g of LiOH?

Practice Calcium carbide, CaC2, reacts with water to form

acetylene.

1 CaC2 + 2 H2O → 1 C2H2 + 1 Ca(OH)2

a. How many grams of water (H2O) are needed to react with 485g of CaC2?

b. How many grams of CaC2 could make 23.6g C2H2?

Practice Oxygen can be prepared by heating potassium

chlorate:

2 KClO3 → 2 KCl + 3 O2

a. What mass of O2 can be made from heating 125g of KClO3?

b. How many grams of KCl could form from 20.8g KClO3?

BRN

Complete the table using: N2 + 3H2 → 2NH3

Moles N2 Moles H2 →Moles NH3

Excess N2 Excess H2

1.5 4.0 →

→ 4.0 2 0

Limiting and Excess Reactants

KC 10: If you have 2 givens in your problem, it is a limiting reactant problem

KC 11: The reactant that produces the smallest amount of a product is the limiting reactant. This is the reactant that will be used up first in the reaction.

Example How many grams of Cu can be formed when

167.4 g of Fe reacts with 399.2 g of CuCl2?

2 Fe + 3 CuCl2 3 Cu + 2FeCl3

Steps for solving LR problems

KC 12:

1. Write down the givens

2. Use molar mass to convert to moles

3. Use mole ratio from the balanced equation

4. Convert to desired unit

5. The correct answer is the smallest answer as the reaction will stop once one reactant is gone

Limiting and Excess Reactant KC 13: 80.0g Cu reacts with 25.0g S. Determine which is

the limiting reactant and calculate how much Cu2S is formed in grams?

2Cu(s) + S(s) → Cu2S(s)

KC 14: What is the limiting reactant if 65.0g of each reactant is present?

___Zn + ___HCl → ___ZnCl2 + ___H2

Limiting and Excess Reactant

Excess and Percent Yield

KC 15: To find how much excess you have you must take the limiting reactant and solve for the excess reactant. You need to look at what you are given versus what you need.

Excess Reactant - Example

How many grams of Cu can be formed when 167.4 g of Fe reacts with 399.2 g of CuCl2?

2 Fe + 3 CuCl2 3 Cu + 2FeCl3

CuCl2 – limiting reactant

188.5g Cu is formed

How many grams of excess is left over?

Excess Reactant KC 16: 24.5g of barium chloride reacts with 45.2g of

sodium sulfate. Which is the limiting reactant and how much of the excess reactant is left over at the end of the reaction?

___BaCl2 + ___Na2SO4 ___BaSO4 + ___NaCl

Percent Yield

KC 17: % yield = actual yield x 100

theoretical yield

KC 18: Actual yield must be found experimentally. It is recognized by words like “produced” and “formed”

KC 19: Theoretical yield is done using stoichiometry. It is a prediction and will always be done using math.

Percent Yield KC 20: A student calculated she should obtain 28g of a

substance. In the experiment, 25g was produced. What is the percent yield of the experiment?

Percent Yield - Example 167.4 g of Fe reacts with 399.2 g of CuCl2 to form

170.3g of copper. What is the percent yield of copper?

2 Fe + 3 CuCl2 3 Cu + 2FeCl3

Practice KC 21: 11.2g of nickel (II) sulfide reacts with 5.43g of

oxygen producing 4.97g of nickel (II) oxide. What is the percent yield of this reaction?

_____NiS2 + _____O2 → _____NiO + _____SO2

Practice KC 22: You are given 0.45g of Al(OH)3 and 0.55g of

H2SO4. The reaction produces 0.15g of water. What is the percent yield of this reaction?

____Al(OH)3 + _____H2SO4 → _____Al2(SO4)3 + _____H2O

Practice KC 23: You are given 3 moles of lithium and 3 moles of

nitrogen. The reaction produces .5 moles of lithium nitride. What is the percent yield of this reaction?

____Li + _____N2 → _____Li3N