Stoichiometry PowerPoint

The Mole and

StoichiometryThe Avagadro Mystery Revealed

“Mole” One mole represents a certain number of something in

a chemical reaction

Similar counting words=

Dozen for 12 of something

Pair for 2 of something

Gross for 144 of something

A “mole” is equal to 6.02 X 1023 of something

602, 000, 000, 000, 000, 000, 000, 000

How Big is a Mole?

Avagadro’s Number

The number of atoms

or molecules in one

mole of a substance

Avagadro’s Number is

equal to 6.022*1023

atoms or molecules

Molecular Mass vs. Molar

MassMolecular Mass

Mass of one molecule of a substance in amu

Remember, we already talked about atomic

mass with the unit of amu

Molar Mass

mass of one mole of a substance

Example:

Molecular Mass

of H20 = 18 amu

1 molecular mass amu = 1 molar mass gram

Example:

if H20 has a molecular

mass of 18amu then

H2O has a molar mass of

18 g/1 mole

1 hydrogen (H) = 1 amu x 2 = 2amu

1 oxygen (O) = 16 amu

Molecular Mass

Calculations

Numbers to know:

Iron’s atomic mass is 56 amu

Carbon’s mass is 12 amu

Oxygen’s mass is 16 amu

Calculate the MOLECULAR mass of:

1. Carbon monoxide (CO)

2. Carbon dioxide (CO2)

3. Iron (III) oxide (Fe2O3)

Molar Mass

Calculations

Whole group

All of the numbers that we pull from the periodic table

have a unit of “amu” or “grams/1 mole”.

Calculate the MOLAR mass of:

1. Carbon monoxide (CO)

2. Carbon dioxide (CO2)

3. Iron (III) oxide (Fe2O3)

Molar Mass

Partner Practice

Calculate the molar mass of:

1. H2O

2. CH4

3. H2CO3

4. C6H12O6

StoichiometryWhy do we need to balance

equations?

How does this connect to our

Chemical Bonding unit?

How can we solve problems using

stoichiometry?

Balancing Equations

Example:

__ Al + __ O2 __ Al2O34 3 22 2

The equation is now balanced

What do balanced

equations tell us?

Example:

1 C2H4O2 + 2 O2 --------> 2 CO2 + 2 H2O

a. Number of moles are bold and underlined.

b. Reactants on the left. Products on the right.

c. We can figure out the molar mass of each.

d. Think of it as an If/Then statement

If/Then…

Example:

1 C2H4O2 + 2 O2 --------> 2 CO2 + 2 H2O

1. IF we have 1 mole of C2H4O2, THEN we will

make 2 moles of CO2

2. IF we end up with 2 moles of H2O, THEN we

started with 2 moles of O2

3. Try your own. Any combination is fine because

they are all related in these ratios.

4. And you can do the same in relating each molar

mass!

Stoichiometry ActivityRemember converting units? Why was this

important?

5 pounds = ____ kilograms

2.2 pounds

1 kilogram

1 kilogram

2.2 pounds

1 kilogram

2.2 pounds

x 2.272

Stoichiometry Activity

• Stoichiometry is important because

it allows us to relate products and

reactants mathematically (just like

our if/then statements)

Stoichiometry – Moles to

Grams

Question: How many grams of CO there in 2.1

moles of CO?

1. What do we have and what do we want?

Have – moles of CO

Want – grams of CO

2. We do this with our “molar mass” card

56 g CO

2 mole CO

1 mole CO

28 g CO

28 g CO

1 mole CO

2.1 moles of CO = ___

grams of CO

28 g CO

1 mole CO

59

__ Fe2O3 + __ CO __ Fe + __ CO2

1. You MUST always do is check if the

equation is balanced and balance it if it is not!

Question: How many moles of carbon monoxide

(CO) are required to react completely with 1.75

moles of iron (III) oxide (Fe2O3)?

Stoichiometry - Mole to Mole





Fe2O3 + 3 CO 2 Fe + 3 CO2

2. Use the question to determine what you have

1.75 moles of Fe2O3

3. Use the question to determine what you want to know

Moles of carbon monoxide

3 mole CO

1 mole Fe2O3




1.75 moles Fe2O3 = ___ moles

of CO

4. Figure out the conversion factor (card) that gets

you from the units you have to the units you want


1 mole Fe2O3

3 moles CO

Fe2O3 + 3 CO 2 Fe + 3 CO2

2 mole Fe

1 mole Fe2O3

3 mole CO

1 mole Fe2O3

5.25

OUR ROAD MAP

What have we learned so far?

2 A + B A2B

Grams A Moles A Moles B Grams B

Now, think of every arrow as a conversion ratio

• Converting grams of A to moles of A requires one

ratio

• Converting moles of A to moles of B requires one

ratio

• Converting grams of A to moles of B requires two

ratios

• Converting grams of A to grams of B requires three

ratios

In this class, you will never need more than three ratios

Stoichiometry

Question: How many grams of CO2 will be

produced from 17 grams of Fe2O3?

Fe2O3 + 3 CO 2 Fe + 3 CO2

For this you will have three steps:

1. Grams of Fe2O3 to moles of Fe2O3

2. Moles of Fe2O3 to moles of CO2

3. Moles of CO2 to grams of CO2

Molar Mass

Molar Mass

Balanced Reaction

Ratios come from:

Try it in your groups!

What are the

Questions?

Science

Stoichiometry PowerPoint