The MoleThe Mole

1 dozen =1 gross =

1 ream =

1 mole =

12

144

500

6.02 x 1023

That is a REALLY BIG number…

A mole is also called A mole is also called Avogadro’s NumberAvogadro’s Number

6.02 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro (1776-1855).

Amadeo Avogadro

I didn’t discover it. Its just named after

me!

The MoleThe Mole•So how do we use the mole in Chemistry?

•There are exactly 12 grams of carbon-12 in one mole of atoms of carbon-12. (6.02 x 1023 atoms)

•There are 6.94 grams of lithium in one mole of atoms of lithium.

•Go count em’ and mass em’

•Notice, these are called atomic weights on

your periodic charts (but this really isn’t a weight…)

Using the MoleUsing the Mole

•We use the mole to convert a measured mass of an element to find the # of atoms that are present.

•Ex: Mass 12g of carbon and you know you’ll have 1 mole of carbon which is 6.02 x 1023 atoms of

carbon. (cool, eh?)

•This is much easier than trying to count individual atoms!!!

Calculations with Moles:Calculations with Moles:Converting moles to gramsConverting moles to grams

How many grams of lithium are in 3.50 moles of lithium?

3.50 mol Li= g Li

1 mol Li

6.94 g Li24.3

There are 24.3 grams of lithium in 3.50 moles of lithium.

Calculations with Moles:Calculations with Moles:Converting grams to molesConverting grams to moles

How many moles of lithium are in 18.2 grams of lithium?

18.2 g Li= mol Li

6.94 g Li

1 mol Li2.62

There are 2.62 moles of lithium in 18.2 grams of lithium.

Calculations with Moles:Calculations with Moles:Using Avogadro’s NumberUsing Avogadro’s Number

How many atoms of lithium are in 3.50 moles of lithium?

3.50 mol Li = atoms Li

1 mol Li

6.022 x 1023 atoms Li 2.11 x 1024

There are 2.11 x 1024 atoms of lithium in 3.50 moles of lithium.

Calculations with Moles:Calculations with Moles:Using Avogadro’s NumberUsing Avogadro’s Number

How many atoms of lithium are in 18.2 g of lithium?

18.2 g Li

= atoms Li

1 mol Li 6.022 x 1023 atoms Li

1.58 x 1024

6.94 g Li 1 mol Li

(18.2)(6.022 x 1023)/6.94

Read 6.2-6.3, pages 159-164

Page 164, do Focus questions 6.1-6.3, #1-4

Page 188, question 8 & 9, problem 10