Limiting Reactants in Chemical Reactions

Introduction

• Definition of a limiting reactant.
• Impact of limiting reactant on the amount of products.
• Topic is higher level chemistry.

Key Concepts

Chemical Reactions

• Example Reaction: Magnesium + Chlorine → Magnesium Chloride.
  • Balanced equation: 1 mole of Magnesium reacts with 1 mole of Chlorine to form 1 mole of Magnesium Chloride.
• Reactants: Starting materials in reactions (e.g., Magnesium and Chlorine).
• Products: Substances formed in reactions (e.g., Magnesium Chloride).

Limiting vs. Excess Reactants

• Limiting Reactant: The reactant that's completely used up in the reaction.
  • Determines the amount of product formed.
• Excess Reactant: The reactant that remains after the reaction is complete.

Example Calculations

Magnesium and Chlorine Reaction

• If 0.5 mol of Magnesium is used with 1 mol of Chlorine:
  • Magnesium is the limiting reactant.
  • Chlorine is the excess reactant.
  • Results: 0.5 mol of Magnesium Chloride formed.

Zinc and Iodine Reaction

• Question: How many moles of Zinc Iodide are produced with 0.5 mol of Zinc and 1 mol of Iodine?
  • Reaction: 1 mole of Zinc reacts with 1 mole of Iodine to produce 1 mole of Zinc Iodide.
  • Zinc is the limiting reactant, so 0.5 mol of Zinc Iodide is formed.
  • Mass Calculation:
    • Relative formula mass of Zinc Iodide = 319
    • Mass = 0.5 mol × 319 = 159.5 grams

Hydrochloric Acid and Sodium Chloride Reaction

• Setup: 1 mole of Hydrochloric Acid reacts with 1 mole of Sodium Chloride.
• If only 0.25 mol of Hydrochloric Acid is used:
  • Hydrochloric Acid is the limiting reactant.
  • 0.25 mol of Sodium Chloride is formed.
  • Mass Calculation:
    • Relative formula mass of Sodium Chloride = 58.5
    • Mass = 0.25 mol × 58.5 = 14.6 grams

Copper Sulfate and Magnesium Reaction

• Question: How many moles of Copper are produced with 0.5 mol of Copper Sulfate and 1 mol of Magnesium?
  • Equation: 1 mole of Copper Sulfate reacts with 1 mole of Magnesium to make 1 mole of Copper.
  • Copper Sulfate is the limiting reactant, resulting in 0.5 mol of Copper.
  • Mass Calculation:
    • Relative atomic mass of Copper = 63.5
    • Mass = 0.5 mol × 63.5 = 31.75 grams

Conclusion

• Understanding limiting reactants is crucial for predicting the outcomes of chemical reactions.
• Further practice questions are available in the provided revision workbook.