Bling Bling: if I were to give each of you one atom of gold for every second that has elapsed since the Dinosaur’s went extinct 65 million years ago,

how much gold would you have?

Moles

• Not to be confused with this very happy individual.

• In Chemistry a mole is defined as 6.022x1023 particles of a substance.

How many eggs are in a dozen?

• How many apples are there in a dozen?

• If a dozen students get detention, how many students have detention?

• Dozen = 12 units

Moles

• 6.022 x 1023 is known as Avogadro’s number.

• Just as a dozen of any substance equals 12 units of that substance, a mole of any substance equals 6.022 x 1023 units of that substance.

Avogadro’s number is a MEASURED number.

• Avogadro: equal volumes of different gases at STP have the same number of particles

• Avogadro’s Number is the number of atoms in 12.01 grams of carbon.

• If we know the charge of one electron and the total charge of one mole of a substance very accurately, we can calculate the number of electrons in a mole of electrons.

MOLAR MASS

1s22s22p63s23p64s23d6

26

FeIRON

55.85

• The atomic mass of iron is 55.85 AMUs.

• This number also represents the molar mass of Iron.

• Iron has a mass of 55.85 grams per mole.

MOLAR MASS

1s22s22p63s23p64s23d6

26

FeIRON

55.85

This is the molar mass of any single element

Unit: g/mol

What is the molar mass of

• Gold• Mercury• Argon• Oxygen• Sulfur• Hydrogen

What is the molar mass of

• Gold• Mercury• Argon• Oxygen• Sulfur• Hydrogen

• 197g/mol• 200.6g/mol• 39.95g/mol• 32g/mol (diatomic)• 32.07g/mol• 2g/m (diatomic)

Concept Check

• How many atoms are there in a mole of gold atoms?

• How many atoms are there in a mole of silver atoms?

79

AuGold

197

47

AgSilver

107.9

Concept Check

• How many atoms are there in a mole of gold atoms?

• How many atoms are there in a mole of silver atoms?

79

AuGold

197

47

AgSilver

107.9

1 mol = 6.022 x1023 units

Give me One Mole of Iron

If I asked you for one mole of iron, how would you do it?

Weigh out 55.85g of iron

• How many atoms of iron would you be giving me?

• A mol is defined as 6.022 x 1023 particles

26

FeIRON

55.85

Give me 3.63 moles of iron?

If I asked you for 3.63 moles of iron, how would you do it?

The same way you would give me 4 dozen of something

units 48dozen 1

units 12dozen 4

By Using Conversion Factors

Converting 3.63 Moles Fe to grams

Fe 202.7gFe mol

Fe 55.85gFe 3.63mol

How many moles is 512 grams of iron?

We solve this again using conversion factors and the molar mass of iron.

Converting 512g Fe to moles.

Fe 9.17molFe 55.85g

Fe 1molFe 512g

How many atoms are in 9.17mol Fe?

Fe atoms10 x 55.2

Fe 1mol

Fe atoms 10 x 6.022Fe 9.17mol

23

23

How many moles are in 25 x 1024 atoms of Fe?

Fe 41.5mol

Fe atoms 10 x 6.022

Fe 1molFe atoms 10 x 25

2324

Mole Worksheets

• 1, 2

Compounds have Molar Mass

H20

H H O

1g/mol 1g/mol 16g/mol

1g/mol + 1g/mol + 16g/mol = 18g/mol

Table Salt

NaCl

Na+ Cl-

23g/mol 35.5g/mol

23g/mol + 35.5g/mol =58.5g/mol

Molar Mass of Sucrose

C12H22O11

C H O

12(12g/mol) 22(1g/mol) 11(16g/mol)

12(12g/mol) + 22(1g/mol) + 11(16g/mol) = 342.3g/mol

Molar Mass of Magnesium Nitrate

Mg(NO3)2

Mg N O

24.3g/mol 2(14.01g/mol) 6(16g/mol)

24.3g/mol + 2(14.01g/mol) + 6(16g/mol) = 148.3g/mol

Mole worksheet

• 3

Molecular Mass

• Molar mass is for the average atomic mass but molecular is for a single molecule but atoms come in different isotopes….

How many moles is 512g of water?

• Convert 512g H20 ---> moles

€

512g H2O∗1mol

18g= 28.4mol H2O

We can Convert Molecules

• Convert 7.5mol H20 ---> grams

OH g351OH 1mol

OH 18gOH 7.5mol 2

2

22

Activity: 1 Cup of Water ~236ml

• How many grams is it?

• What is its molecular mass?

• How many moles is it?

• How many molecules of H2O are there?

• How many total atoms?

• All you need for this is a periodic table and a calculator

Worksheet

• 4

Moles and Volume at STP

STP = Standard Temperature and Pressure

TEMPERATURE: 273.15 K (0 °C, 32 °F)

PRESSURE: 100 kPa (14.504 psi, 0.987 atm, 1 bar).

Remember: volume is proportional to temperature!

Calculating Gas Density

• What is the density of ammonia gas, NH3, at STP?

• First we need the molar mass for ammonia;

14.01 + 3(1.01) = 17.04 g/mol

• The molar volume NH3 at STP is 22.4 L/mol.

• Density is mass/volume:

= 0.761 g/L17.04 g/mol22.4 L/mol

Calculating Gas Density

• What is the density of, O2, at STP?

• First we need the molar mass for O2;

2(16g/mol) = 32 g/mol

• The molar volume O2 at STP is 22.4 L/mol.

• Density is mass/volume:

= 1.4 g/L32 g/mol22.4 L/mol

Calculating Gas Volume• What is the Volume of 5 moles of He at STP?

• First we need the molar mass for He;

He = 4 g/mol

• The molar volume of He at STP is 22.4 L/mol.

He 112LHe 1mol

He 22.4LHe 5mol

Calculating Moles From Volume

• How many moles is 5 Liters of N2 gas at STP?

• The molar volume of N2 at STP is 22.4 L/mol.

22

22 N 0.223mol

N 22.4L

N 1mol N 5L

Molar Mass of a Gas• We can also use molar volume to calculate the

molar mass of an unknown gas.

• 1.96 g of an unknown gas occupies 1.00L at STP. What is the molar mass?

• We want g/mol, we have g/L.

1.96 g1.00 L

22.4 L1 mole× = 43.9 g/mol

Mole Unit Factors

• We now have three interpretations for the mole:

– 1 mol = 6.02 × 1023 particles

– 1 mol = molar mass

– 1 mol = 22.4 L at STP for a gas

• This gives us 3 unit factors to use to convert between moles, particles, mass, and volume.

Mole-Volume Calculation

• A sample of methane, CH4, occupies 4.50 L at STP. How many moles of methane are present?

• We want moles, we have volume.

• Use molar volume of a gas: 1 mol = 22.4 L

4.50 L CH4 × = 0.201 mol CH4

1 mol CH4

22.4 L CH4

Mass-Volume Calculation

• What is the mass of 3.36 L of ozone gas, O3, at STP?

• We want mass O3, we have 3.36 L O3.

• Convert volume to moles then moles to mass:

= 7.20 g O3

3.36 L O3 × ×22.4 L O3

1 mol O3 48.00 g O3

1 mol O3

Molecule-Volume Calculation

• How many molecules of hydrogen gas, H2, occupy 0.500 L at STP?

• We want molecules H2, we have 0.500 L H2.

• Convert volume to moles and then moles to molecules:

0.500 L H2 ×1 mol H2

22.4 L H2

6.02×1023 molecules H2

1 mole H2

×

= 1.34 × 1022 molecules H2

Conclusions

• Avogadro’s number is 6.02 × 1023 and is one mole of any substance.

• The molar mass of a substance is the sum of the atomic masses of each element in the formula.

• At STP, 1 mole of any gas occupies 22.4 L.

Conclusions Continued• We can use the following flow chart for mole

calculations:

Bling Bling: if I were to give each of you one atom of gold for every second that has elapsed since the Dinosaur’s went extinct 65 million years ago,

how much gold would you have?