Stoichiometry & the Mole

What is stoichiometry?

• How many whos are the same as 12 mabees? (1 who = 5 mabees)

• 12 mabees x 1 who = 2.4 who

• 1 5 mabees

Practice

1 whosits = 3 whatever

211 whosits = 12.5 farts

75 farmvilles = 1 no sleep

110 mafia wars = 2 no sleeps

6.02 whosits = 1 mole

20 farts = 1 ROFL

1 mole = 2.5 mice

Questions

1. How many farmvilles equal 4 no sleeps?

2. How many farts in 367 whosits?

3. How many mice in 12.04 whosits?

4. How many moles equal 15 ROFL?

Answers

1. 300 farmvilles

2. 21.7 farts

3. 5.000 mice

4. 840 moles

The Mole Conversion Factor

6.02 x 1023 units = 1 moleEx 6.02 x 1023 pencils = 1 mole of pencils

Ex. 12 eggs = 1 dozen eggs

Ex. 6.02 x 1023 thumb tacks = 1 mole thumb tacks

Dimensional Analysis Review

• How many seconds are in 5.0 hours?

• 5.0 hr

• 5.0 hr x 60 min x 60 sec = 18000 sec

1 hr 1 min

Stoichiometry

• Stoichiometry is just a long word for changing units in chemistry

• If you can do Dimensional Analysis, you can do stoichiometry

The Mole

• Chemists need a convenient method for counting accurately the number of atoms, molecules, or formula units in a sample of a substance.

• The mole, commonly abbreviated mol, is the SI base unit used to measure the amount of a substance.

The Mole

• A mole of anything contains 6.0221367 x 1023 representative particles.

• A representative particle is any kind of particle such as atoms, molecules, formula units, electrons, or ions.

• In this class, Avogadro’s number will be rounded to three significant figures— 6.02 x 1023.

Conversion Factor #1

Mole – Representative Particle Calculations

• Calculate the number of atoms in 3.50 moles of copper

• Start with your given

• 3.50 mol Cu

• Draw your line

• 3.50 mol Cu x _________

Mole – Representative Particle Calculations

• Place the conversion factors

• 3.50 mol Cu x 6.02 x 1023 atoms

1 mol

• Work the problem

• 2.11 x 10 24 atoms Cu

Mole – Representative Particle Calculations

• How many moles of MgO are in 9.72 x 10 23 molecules of MgO?

• 1.61 mol MgO

Stoichiometry

• Using the methods of stoichiometry, we can measure the amounts of substances involved in chemical reactions and relate them to one another.

Conversion Factor # 3

# Moles A

# Moles B

The #’s in front of A & B MUST come from the balanced chemical equation

Mole – Mole Relationship

• 4 Fe + 3O2 2Fe2O3

• 4 mol Fe / 3 mol O2

• 4 mol Fe / 2 mol Fe2O3

• 3mol O2 / 2 mol Fe2O3

• If we have 8 moles of Fe, we will produce 4 moles of Fe2O3.

Mole – Mole Relationship

• 4 Fe + 3O2 2Fe2O3

• How many moles of Fe2O3 can we form from 5.0 mol of Fe?

• 5.0 mole Fe x 2 mol Fe2O3

4 mol Fe

• 2.5 mol Fe2O3