What’s up with the Mole?

How do we measure matter?By weight:We buy bananas by the _______________.

By volume:Milk is sold by the ____________________.

By counting:There are ________ students in class.

pound

gallon

Chemical Quantities

Many words are used to express a specific quantity. Pair = Dozen =

2

12

How do we measure matter?• What if I wanted to know how many ATOMS

were in this copper penny? Would you like to count? Could you?

Avogadro’s Number• You can count particles if you introduce a term

that represents a specified number of particles.

• In chemistry, the term used to express a specific number of particles is a mole.

Avogadro’s Number• 1 mole = 6.02 x 1023 particles

• That’s 602,000,000,000,000,000,000,000602,000,000,000,000,000,000,000

• A very large number!

Avogadro’s Number

This number is known as Avogadro’s number, named after Amedeo Avogadro (an Italian physicist and mathematician).

1 mole of hockey pucks would equal the mass of 1 mole of hockey pucks would equal the mass of the moon!the moon!

1 mole of pennies would cover the Earth 1/4 mile 1 mole of pennies would cover the Earth 1/4 mile deep!deep!

Representative ParticlesRepresentative particles are units used to measure the number of particles in a sample of an element or compound.

Substance Representative Particle

element atom

covalent compound molecule

ionic compound formula unit

Representative ParticlesWhat is the representative particle for each of these substances?

•copper

•sodium chloride

•water

atom

molecule

formula unit

MOLE• A mole is the SI unit that measures the

amount of a substance.

• A mole can be related to: • number of particles•mass• volume of a gas

mass in grams using the periodic

table

Avogadro’s number of particles

22.4 L of a gas

one mole

MOLE• Use dimensional analysis to convert:

– moles to molecules– moles to atoms– moles to formula units– moles to grams– grams to atoms– and many more….

MOLEWhen converting between moles and particles, the conversion factor to remember is:

1 mol = 6.02 x 1023 particles

The particle unit can be atoms, molecules, or formula units.

Mole/Particle Examples

1. How many moles are in 3.25 X 1020 atoms of lead?

3.25 x 1020 atoms Pb

1 mol = 6.02 x 1023 atoms

6.02 x 1023 atoms Pb

1 mol Pb

= 5.398671 x 10-4 = 5.40 x 10-4 mol Pb

Mole/Particle Examples

2. How many molecules are there in 8.3 moles of sugar (C12H22O11)?

8.3 mol C12H22O11

1 mol = 6.02 x 1023 molecules

6.02 x 1023 molec. C12H22O11

1 mol C12H22O11

= 5.0 x 1024 molec. C12H22O11= 4.9966 x 1024

Mole/Particle Examples

3. How many atoms are in 0.425 mol sulfur?

0.425 mol S

1 mol = 6.02 x 1023 atoms

6.02 x 1023 atoms S

1 mol S

= 2.56 x 1023 atoms of S

= 2.5585 x 1023

Mole/Particle Examples

4. How many moles are in 5.42 x 1022 formula units of NaCl?

5.42 x 1022 Form. U NaCl

1 mol = 6.02 x 1023 atoms

6.02 x 1023 Form. U NaCl

1 mol NaCl

= 0.090033222 = 0.0900 mol NaCl

Molar Mass

molar mass – the mass in grams of one mole of an element or compound.

Terms that Describe the Mass of a Substance

• Atomic mass – mass of one atom of an element (unit = amu)

• Molecular mass - mass of one molecule of a covalent compound (unit = amu)

• Formula mass - mass of one formula unit of an ionic compound (unit = amu)

• Molar mass - mass of one mole of an element or compound (unit = g/mol).

Molar MassTo calculate molar mass:

1. Obtain all of the masses of the involved elements from the periodic table.

2. Multiply each element’s mass by the subscript.3. Add the resulting products.4. Round the answer to the proper number of

decimal places.

Molar Mass of Element Examples

• Aluminum =

• Zinc =

26.982 = 26.98 g/mol

65.38 g/mol

Molar Mass of Compounds Examples

• Diphosphorus pentaoxide P2O5

P = O =

30.97415.999

X 2X 5

= 61.948= 79.995 +

141.943 = 141.94 g/mol

Molar Mass of Compounds Examples

• Aluminum Hydroxide Al(OH)3

Al = O =

26.98215.999

X 1X 3

= 26.982= 47.997

+

78.003 = 78.00 g/molH = 1.008 X 3 = 3.024

+3 -1

Molar Mass of Compounds Examples

• Barium phosphate Ba3(PO4)2

Ba = P =

137.328 30.974

X 3X 2

= 411.984= 61.948

+

601.924 = 601.92 g/molO = 15.999 X 8 = 127.992

+2 -3

Moles to Mass

• Use dimensional analysis to convert –moles to mass or mass to moles.

• Mass unit = grams• Conversion Factor to Remember:– 1 mol = molar mass of the element or compound(molar mass = g/mol) found on the periodic table

Moles to Mass Examples

• How many moles of carbon are in 26 g of carbon?

26 g of C

Carbon: 1 mol = 12.01 g (from PT)

1 mol of C

12.01 g of C

= 2.2 mol of C

= 2.164862614

Moles to Mass Examples

• How many grams are there in 2.37 moles of CO2?

2.37 mol CO2

C = 12.011 x 1O = 15.999 x 2

44.01 g CO2

1 mol CO2

= 104 g CO2

= 104.3037

= 12.011= 31.998 +

44.009 g = 1 mol

Moles to Mass Examples

• How many moles are present in 142.1 grams of NaCl?

142.1 g NaCl

Na = 22.990 x 1 Cl = 35.453 x 1

1 mol NaCl58.44 g NaCl

= 2.432 mol NaCl

= 2.43155373

= 22.990= 35.453 +

58.443 g = 1 mol

Moles to Mass Examples

• How many grams are in 3.34 moles of potassium bromide?

3.34 mol KBr

K = 39.098 x 1Br = 79.904 x 1

119.00 g KBr1 mol KBr

= 397 g KBr= 397.46

= 39.098= 79.904 + 119.002 g = 1 mol

+1 -1KBr

Molar Volume of a Gas

• The volume of a gas changes as the temperature and pressure change, so the volume is usually measured at standard temperature and pressure.

• STP = abbreviation for standard temperature and pressure

• Standard temperature = 0oC = 273 K• Standard pressure = 1 atm or 101.3 kPa

Molar Volume of a Gas

• At STP, one mole of any gas occupies the same volume: 22.4 L.

Molar Volume of a Gas

• Use dimensional analysis to convert:–volume (liters) to moles–or moles to volume (liters)

• Conversion Factor to Remember:–1 mole = 22.4 L

Molar Volume of a GasExamples

• Determine the volume, in liters, of 0.60 mol SO2 gas at STP.

Molar Volume of a GasExamples

• Assuming STP, how many moles are in 67.2 L SO2?

Molar Volume of a GasExamples

• How many moles are in 1.0 x 103 L of C2H6?

Molar Volume of a GasExamples

• What is the volume at STP of 3.20 x10-3 mol CO2?

Mole Calculations Learned

MOLES# of Particles

(atoms, molecules,

formula units)

Mass (grams)

Liters of gas at STP

1 mol = 6.02 x 1023 particles

1 mol = 22.4 L

1 mol = mass from Periodic

Table