2.2.4—Activation energy (Ea)

$Ea = minimum kinetic energy for an effective collision$

A Maxwell–Boltzmann curve shows the distribution of particle kinetic energies. At higher temperature the peak is lower and shifts right; the area beyond Ea is larger, so more particles can react.

Two Maxwell–Boltzmann curves for the same number of particles have equal total area. At higher T the curve is broader with a lower peak and a larger area to the right of a fixed Ea line; the peak does not move to Ea and no particle count is lost.

Representative question

[Maximum number: 3]

Explain why the reaction rate increases with temperature, adding annotations to the following Maxwell-Boltzmann graph to assist your explanation.

Explanation:

Retrieve the route: measure a tangent rate, explain effective collisions, map rate factors, read Ea and energy profiles, evaluate mechanisms, determine molecularity and orders, calculate k, then use Arrhenius gradient and intercept for Ea and A.

Check tangent versus average slope, energy versus orientation, barrier labels, intermediate versus transition state, one-variable trial comparisons, order-dependent units, kelvin temperature and the signs of gradient and Ea.

2.2.4—Activation energy (Ea)

Activation Energy and Maxwell–Boltzmann Curves

Interpreting Maxwell–Boltzmann Distributions

Assessment in practice

Rate and Mechanisms Summary

Question 1