Introduction the the Mole

Introduction to the Mole

Scribe: Mary L

Date: September 9th, 2013

To start off class today, Mrs Friedmann went over the 3.1-3.2 web assign worksheet that was assigned for homework last night.  This was checked in, but not collected.  There is an answer key posted under Unit Two Keys on moodle.

MOLES AND MOLAR MASS

Mrs. Friedmann went over a powerpoint on moles for the rest of class.  You can find the powerpoint under Unit 2 Notes in moodle.  

We learned today that atoms are so small that we can only work with them in very large amounts.  We find out how many atoms there are by weighing the samples.  Moles let us work with grams to use weight to find the number of atoms in a sample.  

Let's take Copper,

Copper has an atomic mass of 63.55, if we have 63.55 grams of copper, we have 6.02 * 10^23 atoms of copper, or one mole of copper.  

The molar mass of an element is the same as its average atomic mass.

Examples:

12.01 g Carbon= 1 mole of Carbon

65.39 g Zinc= 1 mole of Zinc

30.97 g Phosphorous= 1 mole of phosphorous

Just like 2 is a pair, and 12 is a dozen, 6.02 * 10^23 is a mole

Now, let's talk about molecules:

Since compounds are not on the periodic table, we cannot find their average atomic mass

To calculate one mole of a compound, we must find the mass of the whole molecule.  You do this by adding up the average atomic masses of all the atoms in the compound

Example:

Water has two hydrogen atoms and one oxygen atom

mass of H: 1.01

mass of O: 16.00

So: (2 * 1.10 g H) + (1* 16.00 g O) =18.02 g H2O

How big is a mole?

To put it into perspective, Mrs Friedmann gave us these examples:

• One mole of watermelon seeds would be found in a watermelon slightly larger than the moon
• One mole of donut holes would cover the earth to a depth of 5 miles
• One mole of pennies would make at least seven stacks that would reach the moon
• If you have a mole of pennies and spend a million dollars a day and died at the age of 100, you would still have 99% of your money after your death.

The homework for tonight is to complete the Calculating Molar Mass Worksheet

The next scribe will be: Cameron B.