Chem — Rate Of Reaction

  • Rate of Reaction

    • Independent variable: changed
    • Dependent variable: measured
    • Controlled variable: constant
    • Rate is inversely proportional to time: faster rate = less time taken.

  • Lesson Objectives

    • Investigate the effect of variables on reaction rate.
    • Interpret experimental data on reaction rates.

  • Speed of Reaction

    • Different reactions have varying rates; speed referred to as rate of reaction.
    • Example: Na + H2O produces NaOH + H2 faster than Rb + H2O.

  • Importance of Reaction Rate

    • Fast reactions in industry yield products quickly.
    • Slow reactions, like decay, help preserve food.

  • Measurement of Reaction Rate

    • Measured by:
    • Time taken for completion
    • Amount of product formed (e.g., gas volume)
    • Reactant disappearing (e.g., mass loss).
    • Example Experiment: Magnesium ribbon in sulfuric acid to measure time.

  • Gas Production Measurement

    • Use gas syringe to measure volume of gas produced over time.
    • Reaction: CaCO3 + HCl produces CaCl2 + CO2 + H2O.
    • Units: (m³/s).

  • Graph Interpretation

    • Steep gradient: fastest reaction, decreases over time as reactants are consumed.
    • A flat line indicates the reaction has stopped.

  • Factors Affecting Reaction Rate

    1. Concentration: Higher concentration increases particle frequency leading to more collisions.
    2. Temperature: Higher temperatures accelerate particles, increasing effective collisions.
    3. Pressure (for gases): Increasing pressure decreases volume, elevating collision frequency.
    4. Surface Area: Smaller particle size increases surface area, enhancing collisions.
    5. Catalysts: Lower activation energy, increasing the rate of reaction.

  • Catalysts

    • Speed up reactions without being consumed.
    • Provide paths of lower activation energy.
    • Examples: Iron in Haber process, enzymes in biological reactions.

  • Enzymes

    • Biological catalysts operating at specific temperatures and pH levels.
    • Examples: Cooking, fermentation, and antibiotic production.