November 24th - Atoms, Molecules, Moles, and More.

Today’s class was a continuation of our learning of moles. We learned how to calculate the number of moes in a given number of molecules, as well as the other way around. We also learned how to calculate the number of atoms of a certain element in a compound. For example, how many oxygen atoms are there in 1.0 moles of water? Well, let’s find out.

Let’s figure out how we will accomplish the task.

First off, we know that there are 6.02 x 10²³ formula units (atoms, molecules, etc) in one mole of a substance. This is commonly known as Avogadro’s number. However, using water, which has the equation HOH, we cannot find the number of atoms simply using this number. This is because we will be finding the number of HOH units, not oxygen atoms. There must be a way to accomplish this? Well, let’s find out.

Each water compound is composed of two hydrogen atoms and one oxygen atom. Knowing there is one oxygen per water, we can form the conversion factor:

1 O atom

1 HOH molecule

Utilizing this conversion factor, we will get the answer of: 6.0 x 10²³.

Too easy, right? Let’s try some more.

A glass contains 5.0 mole of vinegar (CH₃COOH). How many atoms of each element are there in the glass?

5.0 mol x (6.02x10²³/1 mol) x (appropriate conversion factor) 

There are two C atoms, two O atoms, and 4 H atoms.

Simply, multiply the number up top by this. The answers are as follows:  

• 6.0 x 10²⁴ C atoms 
• 6.0 x 10²⁴ O atoms
• 1.2 x 10²⁵ H atoms

Not that hard, eh? Here’s a video to wrap up:

Posted by Andrew.