Effect of Temperature on Reaction Rate
Quick Notes
- Rate of reaction is the change in concentration of a reactant or product per unit time.
- Increasing temperature increases reaction rate because:
- Particles move faster, leading to more frequent collisions.
- More particles have energy ≥ activation energy (Ea), resulting in a greater proportion of collisions being successful.
- Maxwell-Boltzmann distribution shifts right with a lower peak, meaning more molecules have higher energy.
- Even a small temperature increase can cause a large rate increase.
Full Notes
Recap – Rate of Reaction and Temperature
Rate of reaction measures how quickly reactants turn into products.
Defined as:
Temperature has a major impact on reaction rate because it affects molecular motion and energy distribution. The higher the temperature, the more kinetic energy particles have and the more energy they collide with.
Temperature and the Maxwell-Boltzmann Distribution
The Maxwell-Boltzmann distribution shows the spread of molecular energies in a gas.
At higher temperatures:
The curve shifts right as more molecules have higher energy.
The peak lowers because there is now a wider energy distribution.
More molecules have energy ≥ activation energy (Ea) → increased frequency of successful collisions.
Even a small temperature increase causes a large increase in reaction rate because:
- The fraction of particles with E ≥ Ea increases exponentially.
- More successful collisions lead to faster reactions.
Example: A 10°C temperature increase typically doubles the reaction rate.
This is expained in more detail by the Arrhenius Equation, covered later in the course - see Arrhenius Equation.
Summary
| Temperature | Effect on Rate | Explanation |
|---|---|---|
| Higher Temperature | Increases | More molecules have E ≥ Ea |
| Lower Temperature | Decreases | Fewer molecules have E ≥ Ea |
- Raising temperature increases the rate of reaction significantly by increasing particle energy and collision frequency.
- Maxwell-Boltzmann distribution shifts right with a lower peak at higher T.
- Even small increases in temperature cause a large rise in rate because the number of particles with E ≥ Ea rises exponentially.