Integrated Rate Laws

Integrated Rate Laws

  • Integrated rate laws describe how reactant concentrations change over time based on reaction order.

  • Fixed temperatures only, as rate constants vary with temperature.

Key Concepts

Zero-Order Reactions

  • Rate is constant, conc. independent

  • Occurs when reaction is limited by factors e.g. catalysts

    • heterogenous catalysis: rate is proportional to surface coverage fraction

    • enzyme catalysis: enzyme saturation - pseudo zero order

First-Order Reactions

  • Rate is proportional to concentration

  • Steeper gradient: larger rate constant (k)

  • Exponential decay of reactant concentration e.g. ozone decay

Second-Order Reactions

  • Rate is proportional to concentration

  • Slows down at low concentration

  • Involves reactions where two reactant molecules collide e.g. dimerisation

Rate Constants and Their Units

  • Units of rate constants:

    • Zero-order: mol L−1s−1\text{mol L}^{-1} \text{s}^{-1}

    • First-order: s−1\text{s}^{-1}

    • Second-order: L mol−1s−1\text{L mol}^{-1} \text{s}^{-1}

  • Increasing rate constant kk signifies faster reactions.