5.1 Reaction Rates

Reaction Rates

Introduction to Kinetics

• Study of reaction rates

• Different speeds:

  • Fast reactions: methane + oxygen

  • Slow reactions: iron + oxygen.

Measuring Rate of Reaction

• Defined as the rate at which reactants are converted to products over time.

• Depends on factors such as concentration.

• Expressed as:

  • Rate = − ∆[Reactants] / ∆t = ∆[Products] / ∆t

• Units are determined based on the concentration and time.

Equilibrium

• Point where reversible reactions achieve equal forward and backward reaction rates.

• Concentrations of reactants and products remain constant.

Average Rate of Reaction

• Change in concentration of a reactant or product over a specific time interval.

• Calculated as:

  • Average Rate = Change in concentration / Time Interval.

Instantaneous Rate of Reaction

• Change in concentration of a reactant or product at a specific moment.

• Represented by the slope of the tangent line at that point.

• Expressed as:

  • Instantaneous Rate = − ∆[Reactant].

Instantaneous Rate vs. Average Rate

• Graphical representation showing differences over time.

• Instantaneous rate provides specific values at points, while average rate gives overall change over intervals.

Factors Influencing Rate of Reaction

• Concentration: Higher concentration increases reaction rates.

• Temperature: Higher temperatures increase molecular movement, speeding up reactions.

• Surface Area: Increased surface area allows more reaction sites, facilitating faster reactions.

• Catalysts: Substances that speed up reactions without being consumed.

• Pressure: Affects reactions involving gases; increased pressure can enhance rates.