Chemistry Lesson Note On Mole Concept and Stoichiometry

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Topic: Mole Concept and Stoichiometry

Class: SS1

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Specific Objectives:

By the end of the lesson, students should be able to:

1. Define a mole and molar mass.
2. State Avogadro’s number.
3. Use the mole concept in stoichiometric calculations.
4. Solve numerical problems involving mole, mass, volume, and number of particles.

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Instructional Materials:

• Periodic table
• Chart showing Avogadro’s number
• Sample chemical equations
• Whiteboard and markers
• Calculator

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Lesson Content:

Step 1: Definition of Mole

• A mole is the amount of substance that contains as many particles (atoms, molecules, ions, etc.) as there are in 12 grams of carbon-12.
• The number of particles in one mole is known as Avogadro’s number = 6.022 × 10²³ particles.

Step 2: Molar Mass

• The molar mass of a substance is the mass of one mole of that substance, expressed in grams per mole (g/mol).
  • E.g., Molar mass of H₂O = 2(1) + 16 = 18 g/mol

Step 3: Relationship Between Mass, Moles, and Molar Mass

• Formula:

  \text{Number of moles} = \frac{\text{Mass of substance (g)}}{\text{Molar mass (g/mol)}}

Step 4: Avogadro’s Number and Particle Calculations

• Formula:

  \text{Number of particles} = \text{Number of moles} \times 6.022 \times 10^{23}

Step 5: Mole Concept in Stoichiometry

• Stoichiometry involves calculating the quantities of reactants and products in chemical reactions using balanced chemical equations.
• Example:
  Given the reaction:

  2H_2 + O_2 \rightarrow 2H_2O

• If given 4 moles of H₂, how many moles of H₂O will be formed?

  Use ratio 2:2 → Answer = 4 moles of H₂O

Step 6: Solving Typical Problems

Problem 1:
Calculate the number of moles in 36g of water (H₂O).
Solution:
Molar mass of H₂O = 18 g/mol

\text{Moles} = \frac{36}{18} = 2 \text{ moles}

Problem 2:
How many molecules are in 3 moles of oxygen gas (O₂)?

\text{Particles} = 3 \times 6.022 \times 10^{23} = 1.807 \times 10^{24} \text{ molecules}

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Evaluation:

1. Define the term mole.
2. State Avogadro’s number.
3. Calculate the number of moles in 44g of CO₂ (Molar mass = 44 g/mol).
4. How many atoms are in 2 moles of magnesium?
5. In the equation N₂ + 3H₂ → 2NH₃, how many moles of NH₃ will be produced from 5 moles of H₂?

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Homework:

1. Calculate the number of molecules in 0.5 moles of water.
2. How many moles are present in 12g of carbon dioxide (CO₂)?
3. What is the mass of 0.25 moles of NaCl? (Na=23, Cl=35.5)

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Conclusion:

The mole concept provides a bridge between the atomic and macroscopic worlds. Understanding the mole, molar mass, and Avogadro’s number is foundational for mastering stoichiometry and chemical reactions.