Unit 2, Topic 2:

The Mole

Lesson Instructions

Review the learning goals and success criteria for Topic 2: The Mole
- Review the minds on, action, and consolidation sections of the lesson, completing any tasks as outlined.
- Complete the fill-in-the-blanks handouts that have been provided to you. They have been linked below.
- Practice and apply what you've learned by completing the practice tasks outlined at the end of the lesson.

Learning Goals (continued from Topic 1)

I am learning to ...

understand how two atoms of the same element can have different masses
describe what a “mole” is as and how it relates to chemistry
use the concept of a “mole” is conversion calculations

Success Criteria (continued from Topic 1)

I am able to ...

use significant digits appropriately in calculations
describe the term isotope and how it is related to the atomic abundance
describe the concept of the mole as 6.02 × 10²³ particles (such as atoms or molecules) of a sample
use the mole to perform conversion calculations

Minds-On

As it is convenient to count eggs using dozens, chemists also count atoms and molecules using something called a mole. One mole is equal to 6.02 × 10²³ particles. In this lesson, you will be introduced to the mole and its use in some simple calculations.

What is a mole?

No, I'm not talking about the little furry animal. I am talking about a unit of measurement – called the mole. Watch the following video to learn about the concept of the mole in chemistry. Learn the incredible magnitude of the mole – and how something so big can help us calculate the tiniest particles in the world.

Figure 1. The mole and Avogadro's number.

Action

Everyday Counting Units

As described in the previous lesson, we use a variety of everyday counting units. Here are some examples:

Figure 2. A carton of one dozen eggs is equal to 12 eggs.

Figure 3. One ream of paper contains 500 sheets of paper.

Figure 4. One pair of socks contains two socks.

We can use the same type of simplification when we talk about particles.

We say that one mole of particles = 6.02x10²³ particles.

So, if there are two socks, in one pair, then there are 6.02x10²³ particles in one mole.

This number, 6.02x10²³, is known as Avogadro's Number, and is denoted by the symbol N_A .

The Mole and Avogadro's Constant

Okay! So, now we have these two new terms; the mole and Avogadro's Number. So, now what? How do they relate to each other? What do these numbers tell us? Watch the following video of me explaining how we relate Moles and Avogadro's number in calculations.

Mole Calculation Triangle

This a picture of the mole triangle that you will use for all of your calculations. Watch the video below to see how it works.

Note: Although it would be a good idea to memorize this triangle, I will always provide you with a copy of it for assessments. Knowing how to use the triangle to guide you through calculations is essential.

Figure 5. The Mole Calculation Triangle.

Practicing Different Types of Calculations with Moles

Example 3:

A sample contains 1.25 mol of nitrogen dioxide. How many molecules are in the sample?

Example 4:

A sample of aluminum oxide contains 7.71x10²⁴ molecules. How many moles of aluminum oxide are in the sample?

Example 5:

A small pin contains 0.0178 mol of iron, Fe. How many atoms of iron are in the pin?

Try these!

Alright! Now that you've seen how these problems are calculated, please give these a try. Attempt the question before you check the solution.

Problem #1

How many moles of tin (Sn) are equivalent to 1.8066x10²⁴ atoms?

Show the Solution

Problem #2

A sample contains 4.70×10⁻⁴ mol of gold, Au. How many atoms of gold are in the sample?