The Mole

December 2nd, 2008

Units

• Units are fundamental to chemistry

o Important for interpreting information 3 g vs 3 mL vs 3 g/mL What can you determine from these units?

o Can be used to solve problems If you know what units you start with and you know

what you end with you can use units to fill in the middle This is called Dimensional Analysis

Dimensional Analysis    

Allows for the conversion of quantity from one unit to another    •  Simple

o g to mg

• Hardero cubic feet to cubic inches

• Longero m/s to mi/hr

But this isn't chemistry yet....

Exactly!

Math is the fundamental language of science, if you can't communicate clearly with math you will have a difficult time understanding chemistry.

Good communication skills:• Identify important information• Write clear explanations• Check yourself for mistakes

The fundamental unit of Chemistry...THE MOLE!!

What is it?  A just a word that takes the place of anumber, just like we say a dozen instead of writing 12 ora gross instead of 144.

1 mole = 6.022 x 1023

You can have a mole of anything

How many atoms would be in 6 moles?

How many molecules would be in 0.25 moles?

How do Chemists use the mole?

The mole allows us to think about quantities of elements in a size that is easy to picture on the human scale.

A hydrogen atom weighs approximately 1.6726×10−27 kg Can you picture how much that is?

If a mole is 6.022 x 1023 atoms.  How much does a mole of Hydrogen weigh? 

Have you seen this number anywhere before?

The Mole and the Periodic Table

• The number under the atomic symbol is the mass of an element.o Is this the mass of one atom of the element?

• This is the Molar Mass... the mass of one mole of an element

• What is the molar mass of Oxygen?

• What is the molar mass of Water?

• What is the molar mass of Carbon Tetrachloride?

• What is the molar mass of Magnesium Hydroxide?

The Mole and Dimensional Analysis

• How can the mole be used in dimensional analysis?o Converts between moles and atomso Use molar mass to convert between g and mol

• How many moles are in 20 g of Carbon?

• How many moles are in 20g of Carbon Dioxide?