Using Moles to Count Atoms

Introduction

• Objective: Understanding how moles help count the number of atoms in a substance.
• Example: Counting the number of Carbon atoms in a container.

What is a Mole?

• A mole is similar to a dozen but much larger.
• Definition: 1 mole = 6.02 x 10^23 atoms (602 hexillion).

Counting Atoms with Moles

• Atoms are too tiny to count visually.
• Counting out individual atoms in a mole is impractical due to time constraints.
• Instead, we use the concept of molar mass to weigh and determine the number of atoms.

Analogy: Candy Factory

• Scenario: Counting 10,000 jellybeans vs. weighing them.
• Knowing the weight of 10,000 jellybeans allows counting by weight instead of individually.

Moles and Atomic Weights

• Sulfur Example: 1 mole of Sulfur = 32.07 grams.
• Weighing 32.07 grams of Sulfur approximates 602 hexillion atoms without counting.

Using the Periodic Table

• The periodic table provides the molar mass of elements, indicating how much one mole weighs.
• Examples:
  • Carbon: Molar mass = 12.01 grams/mole.
  • Zinc: Molar mass = 65.38 grams/mole.

Application: Determining Number of Atoms

1. Step 1: Weigh the substance to find its mass.
2. Step 2: Determine the number of moles using the formula:
   • Total mass / Molar mass = Number of moles
3. Step 3: Multiply the number of moles by Avogadro's number (6.02 x 10^23) to find the total number of atoms.

Example Calculation

• Given: 31.87 grams of Carbon.
• Molar Mass of Carbon: 12.01 grams/mole.
• Calculate Moles:
  • 31.87 grams / 12.01 grams/mole = 2.654 moles.
• Calculate Atoms:
  • 2.654 moles x 6.02 x 10^23 atoms/mole = 1.60 x 10^24 atoms.

Conclusion

• The mole allows us to count atoms by weighing them rather than counting individually.
• Used scientific notation for ease in calculations.
• This method simplifies the process of determining the number of atoms in a sample.