Video 1

Learning outcomes

At the end of the lesson, students must be able to:

• Define mole in terms of mass of carbon-12 and Avogadro constant, NA.

• Interconvert between moles, mass, number of particles, molar volume of gas at s.t.p. and room temperature.

By definition: 1 atom 12C “weighs” 12 amu

On this scale

1H = 1.008 amu

16O = 16.00 amu

Atomic mass is the mass of an atom in atomic mass units (amu)

Micro Worldatoms & molecules

Macro Worldgrams

Natural lithium is:

7.42% 6Li (6.015 amu)

92.58% 7Li (7.016 amu)

7.42 x 6.015 + 92.58 x 7.016100

= 6.941 amu

Average atomic mass of lithium:

The mole (mol) is the amount of a substance that contains as many elementary entities as there

are atoms in exactly 12.00 grams of 12C

1 mol = NA = 6.0221367 x 1023

Avogadro’s number (NA)

Video 2

Molar mass is the mass of 1 mole of in gramseggsshoes

marblesatoms

1 mole 12C atoms = 6.022 x 1023 atoms = 12.00 g

1 12C atom = 12.00 amu

1 mole 12C atoms = 12.00 g 12C

1 mole lithium atoms = 6.941 g of Li

For any element

atomic mass (amu) = molar mass (grams)

Counting Objects of Fixed Relative Mass

12 red marbles @ 7g each = 84g12 yellow marbles @4g each=48g

55.85g Fe = 6.022 x 1023 atoms Fe32.07g S = 6.022 x 1023 atoms S

Water 18.02 g

One Mole of Common Substances

CaCO3

100.09 g

Oxygen 32.00 g

Copper 63.55 g

1 amu = 1.66 x 10-24 g or 1 g = 6.022 x 1023 amu

1 12C atom12.00 amu

x12.00 g

6.022 x 1023 12C atoms=

1.66 x 10-24 g1 amu

M = molar mass in g/mol

NA = Avogadro’s numberVideo 3

Do You Understand Molar Mass?

How many atoms are in 0.551 g of potassium (K) ?

1 mol K = 39.10 g K

1 mol K = 6.022 x 1023 atoms K

0.551 g K 1 mol K39.10 g K

x x 6.022 x 1023 atoms K1 mol K

=

8.49 x 1021 atoms K Video 4

Molecular mass (or molecular weight) is the sum ofthe atomic masses (in amu) in a molecule.

SO2

1S 32.07 amu

2O + 2 x 16.00 amu SO2 64.07 amu

For any molecule

molecular mass (amu) = molar mass (grams)

1 molecule SO2 = 64.07 amu

1 mole SO2 = 64.07 g SO2

Do You Understand Molecular Mass?

How many H atoms are in 72.5 g of C3H8O ?

1 mol C3H8O = (3 x 12) + (8 x 1) + 16 = 60 g C3H8O

1 mol H = 6.022 x 1023 atoms H

5.82 x 1024 atoms H

1 mol C3H8O molecules = 8 mol H atoms

72.5 g C3H8O1 mol C3H8O

60 g C3H8Ox

8 mol H atoms

1 mol C3H8Ox

6.022 x 1023 H atoms

1 mol H atomsx =

Table Summary of Mass Terminology

Term Definition Unit

Isotopic mass Mass of an isotope of an element amu

Atomic mass

Molecular (or formula) mass

Molar mass (M)

(also called atomic weight)

(also called molecular weight)

(also called gram-molecular weight)

amu

amu

g/mol

Average of the masses of the naturally occurring isotopes of an element weighted according to their abundance

Sum of the atomic masses of the atoms (or ions) in a molecule (or formula unit)

Mass of 1 mole of chemical entities (atoms, ions, molecules, formula units)

Converting cm3 to mole

Video 5

The molar volume of gases

Mole Concept of GasesMolar volume of any gas at STP, Vm = 22.4 dm3mol1 STP = standard temperature and pressureWhere T = 273.15 K P = 1 atm @ 760 mmHg

Amount of gas at STP, n = V, Volume of gas (L)Vm (22.4 dm3 mol1)

Video 6

Example

mol 1.0mole ofNumber

so,

gashydrogen of mol 2.24x 22.4

1 consists dm 2.24

gashydrogen of mol 1 consists dm 22.4

1, Solution

gas.hydrogen of (mole)amount the

calculate ,dm 2.24 isballon theof volume theIf

s.t.p.at gashydrogen with filled isballoon A

3

3

3

mol 0.1 4.22

2.24dm

4.22

)(dm gas of mole ofNumber

2, Solution

13

3

13

3

moldm

moldm

volume

• 1 mole of gas has a volume of 24.0 dm3 at room temperature

At room temperature,

volume of gas (dm3) = number of mole X 24.0 dm3 mol-1