I. Stoichiometric

Calculations

Stoichiometry Stoichiometry

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

Having everything I need for making cookies. 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• Molarity - moles liters soln• Molar volume - moles liters gas

Core step in all stoichiometry problems!!

• Mole ratio - moles moles

4. Check answer.

C. The Mole HillC. The Mole HillC. The Mole HillC. The Mole Hill

Mole Ratio

Molar Mass X

Molar Mass Y

Grams of X Grams of Y

C. Moles of X to Moles of C. Moles of X to Moles of YYC. Moles of X to Moles of C. Moles of X to Moles of YY

1. How many moles of H2O are produced from 10 moles of O2 gas?

10 mol O2 2 mol H2O

1 mol O2

= 20 moles H2O

2H2 + O2 2H2O 10 mol ? mol

Mole Ratio

Day 2

C. Moles of X to Grams of C. Moles of X to Grams of YYC. Moles of X to Grams of C. Moles of X to Grams of YY

How many grams of NaOH are produced

from 5 moles of Na?

2H2O + 2Na 2 NaOH + H2 5 mol ? grams

5 mol Na

2 mol Na

2 mol NaOH

1 mol NaOH

39.98 g NaOH

Mole Ratio

Formula Mass

199.90 g NaOH

=

STEP 1 STEP 2

C. Grams of X to Moles of C. Grams of X to Moles of YYC. Grams of X to Moles of C. Grams of X to Moles of YY

How many moles of water are produced

from 5 grams of oxygen gas? 4 NH3(g) + 5O2(g) 4NO(g) + 6H2O(g)

5 g ? moles

5 g O2

31.98 g O2

1 mol O2

5 mol O2

6 mol H2O = 0.19 mol H2O

Mole RatioFormula Mass

STEP 1 STEP 2

Day 3

C. Grams of X to Grams of C. Grams of X to Grams of YYC. Grams of X to Grams of C. Grams of X to Grams of YY

How many grams of MgO are produced

from 145 g of Mg? 2 Mg + O2 2 MgO 145 g ? g

145 g Mg

24.31g Mg

1 mol Mg

2 mol Mg

2 mol MgO

1 mol MgO

40.30 g MgO

Mole Ratio= 240.37 g MgO

STEP 1 STEP 2 STEP 3

Molar Mass(g/mol)

6.02 1023

particles/mol

MASSIN

GRAMSMOLES

NUMBEROF

PARTICLES

LITERSOF

SOLUTION

Molar Volume (22.4 L/mol)

LITERSOF GASAT STP

Molarity (mol/L)

Practice Problems

D. Stoichiometry PracticeD. Stoichiometry PracticeD. Stoichiometry PracticeD. Stoichiometry Practice

1. 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

D. Stoichiometry PracticeD. Stoichiometry PracticeD. Stoichiometry PracticeD. Stoichiometry Practice

3.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