Introduction to the Mole Counting Atoms

The Mole A special unit used by chemists to express amounts of particles such as atoms, molecules, or ions. The SI unit for amount of substance Abbreviated mol A counting unit, similar to a dozen

Avogadro’s Number The number of particles in a mole has been experimentally determined in a number of ways. The best modern value is x (we will use x ) Amedeo Avogadro’s ideas were extremely important in determining the relationship between mass and numbers of atoms

Just How Big is a Mole? Imagine you have a mole of pennies to count ◦You employ everyone in the world (7 billion people) to help you count. ◦Everyone will count 24 hours a day, seven days a week. ◦Each person counts 1 penny per second 7 billion pennies are counted each second trillion pennies are counted each hour. 600 trillion pennies are counted each day. It would take almost one billion days to count to a mole (6.022 x ). In other words, it would take almost 3 million years, with everyone in the world counting!

Just How Big is a Mole? If you laid out a mole of pennies end to end they would extend to the moon and back 7 times. A mole of aluminum cans would cover the Earth's surface (land and oceans) over 200 miles deep. A mole of chocolate chips would cover the earth over 500 feet deep.

What Would You Do? If you had a mole of pennies in your bank account? With a mole of water?

Video Clip The Mole Concept

Calculations Involving the Mole The mole is used in chemistry primarily to make calculations easier. Since atoms are so small, most calculations would involve incredibly large numbers, therefore the mole is used. We will use the conversion factor method that was introduced in the beginning of the year. (1 mole = x atoms)

Review of Conversion Factors

Sample Problem 1 atoms Ag mol Ag x

Sample Problem 2 atoms Al mol Al x