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Concentration Changes Over Time

The concentration of reactants and products in a chemical reaction changes as the reaction progresses. Studying these changes helps determine reaction rates and mechanisms.

Key Concepts​

  • Rate of Reaction: Change in concentration per unit time
    • Rate = −Δ[Reactant]/Δt = Δ[Product]/Δt
  • Reaction Order: Relationship between concentration and rate
  • Rate Law: Mathematical expression of reaction rate as a function of concentration
    • Example: Rate = k[A]ⁿ[B]ᵐ

Graphical Representation​

  • Reactant concentration vs. time: Typically decreases over time
  • Product concentration vs. time: Typically increases over time
  • Slope of the curve gives the instantaneous rate

Factors Affecting Concentration Changes​

  1. Concentration – Higher reactant concentrations increase collision frequency
  2. Temperature – Higher temperature increases reaction rate
  3. Catalyst – Speeds up reaction without being consumed
  4. Surface Area – Affects reactions with solids

Importance​

  • Understanding how concentrations change over time allows:
    • Prediction of reaction progress
    • Determination of rate laws
    • Insight into reaction mechanisms

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