Stoichiometric Calculations Start Your Book Problems NOW!! Stoichiometry.

Stoichiometric

Calculations

Start Your Book Problems NOW!!

Stoichiometric

Calculations

Start Your Book Problems NOW!!

StoichiometryStoichiometry

A. Proportional A. Proportional RelationshipsRelationshipsA. Proportional A. Proportional RelationshipsRelationships

I have 5 eggs. How many cookies can I make?

3/4 c. brown sugar1 tsp vanilla extract2 eggs2 c. chocolate chipsMakes 5 dozen cookies.

2 1/4 c. flour1 tsp. baking soda1 tsp. salt1 c. butter3/4 c. sugar

5 eggs 5 doz.

2 eggs= 12.5 dozen cookies

Ratio of eggs to cookies

A. Proportional A. Proportional RelationshipsRelationshipsA. Proportional A. Proportional RelationshipsRelationships

StoichiometryStoichiometry• mass relationships between

substances in a chemical reaction• based on the mole ratio

Mole RatioMole Ratio• indicated by coefficients in a

balanced equation

2 Mg + O2 Mg + O22 2 MgO 2 MgO

B. Stoichiometry StepsB. Stoichiometry StepsB. Stoichiometry StepsB. Stoichiometry Steps

1. Write a balanced equation.2. Identify known & unknown.3. Line up conversion factors.

• Mole ratio - moles moles• Molar mass - moles grams

Core step in all stoichiometry problems!!

• Mole ratio - moles moles

4. Check answer.

C. Stoichiometry C. Stoichiometry ProblemsProblemsC. Stoichiometry C. Stoichiometry ProblemsProblems

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

9 mol O2 2 mol KClO3

3 mol O2

= 6 mol KClO3

2KClO3 2KCl + 3O2 ? mol 9 mol

How many grams of KClO3 are req’d to

produce 9.00 mol of oxygen gas?

9.00 molO2

= 735 g KClO3

2 molKClO3

3 molO2

122.55g KClO3

1 molKClO3

? g 9.00 mol


2KClO3 2KCl + 3O2


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

12.0g Cu

1 molCu

63.55g Cu

= 40.7 g Ag

Cu + 2AgNO3 2Ag + Cu(NO3)2

2 molAg

1 molCu

107.87g Ag

1 molAg

12.0 g ? g

II. Stoichiometry in the Real World

II. Stoichiometry in the Real World

Stoichiometry Part IIStoichiometry Part II

A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants

Available IngredientsAvailable Ingredients• 4 slices of bread• 1 jar of peanut butter• 1/2 jar of jelly

Limiting ReactantLimiting Reactant• bread

Excess ReactantsExcess Reactants• peanut butter and jelly


Limiting ReactantLimiting Reactant• used up in a reaction• determines the amount of product

Excess ReactantExcess Reactant• added to ensure that the other

reactant is completely used up• cheaper & easier to recycle


1. Write a balanced equation.

2. For each reactant, calculate the

amount of product formed.

3. Smaller answer indicates:

• limiting reactant

• amount of product


79.1 g of zinc react with 2.25 mol of HCl. Identify the limiting and excess reactants. How many grams of hydrogen gas are formed.

Zn + 2HCl ZnCl2 + H2 79.1 g ? g2.25 mol


79.1g Zn

1 molZn

65.39g Zn

= 2.44 g H2

1 molH2

1 molZn

2.02 gH2

1 molH2



2.02 gL H2

1 molH2

2.25 molHCl

= 2.27 g H2

1 molH2

2 molHCl



Zn: 2.44 g H2 HCl: 2.27 g H2

Limiting reactant: HCl

Excess reactant: Zn

Product Formed: 2.27 g H2

left over zinc

B. Percent YieldB. Percent YieldB. Percent YieldB. Percent Yield

100yield ltheoretica

yield actualyield %

calculated on paper

measured in lab


When 45.8 g of K2CO3 react with excess

HCl, 46.3 g of KCl are formed. Calculate the theoretical and % yields of KCl.

K2CO3 + 2HCl 2KCl + H2O + CO2 45.8 g ? g

actual: 46.3 g


45.8 gK2CO3

1 molK2CO3

138.21 gK2CO3

= 49.4g KCl

2 molKCl

1 molK2CO3

74.55g KCl

1 molKCl

K2CO3 + 2HCl 2KCl + H2O + CO2 45.8 g ? g

actual: 46.3 g

Theoretical Yield:


Theoretical Yield = 49.4 g KCl

% Yield =46.3 g

49.4 g 100 =93.7%

K2CO3 + 2HCl 2KCl + H2O + CO2 45.8 g 49.4 g

actual: 46.3 g

Stoichiometric Calculations Start Your Book Problems NOW!! Stoichiometry.

Documents

Transcript of Stoichiometric Calculations Start Your Book Problems NOW!! Stoichiometry.