(40) GCSE Chemistry Revision "Avogadro's Constant 1"

Introduction to Avogadro's Constant

• Importance for higher students in chemistry

• Avogadro's constant value: 6.02 × 10^23

Understanding Moles and Molecules

Definition of a Mole

• A mole is a shorthand for a large number of particles (atoms or molecules).

• It helps to relate mass of substances to the number of particles.

Calculating Moles of Atoms in Molecules

• Sample Problem: Number of moles of atoms in one mole of water (H₂O).

  • Solution:

    • One molecule of water = 2 Hydrogen + 1 Oxygen = 3 atoms total.

    • Therefore, 1 mole of water = 3 moles of atoms.

Exercises to Practice Moles of Atoms

• Example 1: Methane (CH₄)

  • One molecule of methane = 1 Carbon + 4 Hydrogen = 5 atoms.

  • So, 1 mole of methane = 5 moles of atoms.

• Example 2: Calcium Hydroxide (Ca(OH)₂)

  • One molecule contains 1 Calcium + 2 Oxygen + 2 Hydrogen = 5 atoms.

  • Thus, 1 mole of calcium hydroxide = 5 moles of atoms.

Using Avogadro's Constant to Calculate Number of Atoms

Transition to Atoms Calculation

• Next step: Calculate total number of atoms from moles using Avogadro's constant.

Example Problem: Hydrogen Chloride (HCl)

• Given: 1 mole of HCl = 6.02 × 10^23 molecules.

• Each HCl contains 2 atoms (1 Hydrogen + 1 Chlorine).

• Calculation:

  • Total atoms = 6.02 × 10^23 molecules × 2 atoms/molecule = 1.24 × 10^24 atoms.

Practice Problem

• Example 3: Sodium Oxide (Na₂O)

  • 1 mole of Na₂O = 6.02 × 10^23 molecules.

  • Each Na₂O molecule contains 3 atoms (2 Sodium + 1 Oxygen).

  • Total atoms calculation: total atoms = 6.02 × 10^23 × 3 = 1.86 × 10^24 atoms.

Conclusion and Further Learning

• More practice available in the revision workbook linked in the video.

• Next video will cover more complex uses of Avogadro's constant.