Unit 1 continuedThe Mole!!!

Intro to the Mole

Counting by Mass

The Mole

Molar Mass

Counting Candy: Counting by Mass Sometimes it is inconvenient or even impossible to

count using traditional methods

Small particles

Large numbers of particles

Counting by mass uses the average mass of the particle to calculate a given number of particles

How much candy is in my jar?

Get an average mass (massA)

Get a total mass (masst)

# particles = masst/massa

Atomic Masses and the Mole

You can calculate the given number of atoms using the atomic mass

Atomic mass is the weighted average mass of all the isotopes of an atom

Atomic mass expressed in AMU’s is the mass of 1 atom of that element

The atomic mass expressed in grams is the mass of 1 mole of atoms

…So, what is a mole?

The Mole

Suppose we have a sample of Al with a mass of 26.98g

What mass of Cu would have the same number of atoms?

How about C?

If we were to measure out samples of any elements such that the masses in grams are equal in number to the atomic masses, we will ALWAYS have the same number of atoms!

THAT NUMBER IS CALLED…THE

MOLE!

More Mole

The Mole: the number equal to the number of carbon atoms in 12.01g of carbon. It is associated with a specific number:

Avogadro's Number

6.022x1023 of anything is a mole

Think “dozen”

It is a UNIT!

Molar Mass = mass of 1 MOLE

Element: The molar mass of an element is equal to the atomic mass expressed in grams instead of AMU’s

What is the Molar Mass of

Carbon

Nickel

Oxygen (careful diatomic!)

Compound: The molar mass of a compound is equal to the sum of the molar masses of each element in the compound in the correct ratio.

Calculate the molar mass of:

CO2

NaCl

Pb2(SO4)3

Picture of Molar Mass

A little help please (mole problem flow chart)

Practice!

Calculate the Number of particles (atoms/molecules) in:

2.5 mols Na

76 g K

23 g CO2

1240 mg HBr

Calculate the mass of:

1.0 mols CH4

6.022x1023 atoms of Na

2.4 mols PbNO3

2.3x1022 mlcs H2SO4

More Practice!

Calculate the molar mass of the following:

Molybdenum

Lanthanum

CBr4

HgO

TiO2

MnCl2

PH3

Perform the following calculations:

1.0 moles O2 particles O2

2.6 g Cu moles Cu

4.0x1022 atoms Al moles Al

4.0x1022 atoms Al grams Al

26.2g NaCl moles NaCl

26.2 g NaCl particles NaCl

End the Mole Madness!

Tips to help with mole problems…

In the conversion process, the mole gets a 1

6.022x1023 will ALWAYS be atoms, particles, etc.

Use the molar mass any time you see grams

Let your units tell the story