Edexcel IGCSE Chemistry: Rates of Reaction Summary

Rates of Reaction

• Factors Influencing Reaction Rates:
    - Surface Area
    - Concentration of Solutions
    - Temperature
    - Pressure of Gases
    - Presence of Catalysts

• Rate of Reaction Formulas:
    - Rate of reaction = Amount of reactant used / Time
    - Rate of reaction = Amount of product formed / Time
    - Units: g/s, cm³/s, or mol/s

• Effect of Temperature:
    - Increasing temperature raises reaction rate by increasing particle speed, leading to more frequent and energetic collisions.

• Effect of Pressure:
    - Increasing pressure in gas reactions raises reaction rate by increasing collision frequency.

• Effect of Concentration:
    - Higher concentration of solutions leads to increased collision frequency, thus raising reaction rate.

• Effect of Surface Area:
    - Increased surface area of solid reactants enhances collision frequency and raises reaction rate.

• Role of Catalysts:
    - Catalysts are substances that increase reaction rates without being consumed.   - They provide an alternative pathway with lower activation energy, increasing the number of reacting particles.

• Practical Investigations:
    - Investigate the effect of changing surface area of marble chips and the concentration of hydrochloric acid on their reaction rate.
      - Smaller marble chips (larger surface area) increase reaction rate.
      - Higher hydrochloric acid concentration increases reaction rate.   - Investigate the catalytic decomposition of hydrogen peroxide with different solids.