Conservation of Mass

Introduction

• The objective of this lesson is to understand mass conservation in chemical reactions and calculate masses involved.

Law of Conservation of Mass

• Definition: No atoms are lost or made during a chemical reaction, so the mass of the products equals the mass of the reactants.

Key Terms

• Reactants: Starting materials in a chemical reaction (e.g., magnesium and chlorine).

• Products: Chemicals formed from a reaction (e.g., magnesium chloride).

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Example Reaction

Magnesium and Chlorine Reaction

Chemical Equation: Magnesium + Chlorine → Magnesium Chloride

• Given: 24 grams of magnesium and 71 grams of chlorine.

• Calculating Mass of Products:

  • Total mass of reactants: 24g + 71g = 95g.

  • Mass of magnesium chloride produced = 95g.

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Common Exam Question

• Typical exam format involves calculating product mass using given reactant masses.

Practice Problems

Problem 1: Sodium and Oxygen Reaction

• Given: 92 grams of sodium reacts with 32 grams of oxygen.

• Calculation:

  • Total mass of reactants = 92g + 32g = 124g.

  • Mass of sodium oxide produced = 124g.

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Problem 2: Calcium Carbonate Reaction

• Given: Produces 112 grams of calcium oxide and 88 grams of carbon dioxide.

• Task: Calculate mass of calcium carbonate that reacted.

• Calculation:

  • Total mass of products = 112g + 88g = 200g.

  • Therefore, mass of calcium carbonate = 200g.

Problem 3: Magnesium Oxide Reaction

• Given: Produces 95 grams of magnesium chloride and 18 grams of water with 73 grams of hydrogen chloride.

• Calculation:

  • Total mass of products = 95g + 18g = 113g.

  • Mass of magnesium oxide = 113g - 73g = 40g.

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Conclusion

• Review and practice various mass calculation problems in chemistry.

• Reference to Ovision workbook for additional practice questions.