18.5 Effect of temperature on rate constants

• When temperature is increased

  • Boltzmann distribution shifts to the right, increasing the proportion of particles that exceed the activation energy
  • Particles move faster and collide more frequently, with more particles colliding with the correct orientation to react
• With increasing temperature, the increase in collision frequency is comparatively small compared with the increased proportion of molecules that exceed activation energy
• The Arrhenius equation shows how the rate constant is linked with activation energy, temperature and the pre-exponential factor A
• The Arrhenius equation can be expressed in a logarithmic relationship

  lnk = -Ea/RT + lnA
• Gradient is calculated by -Ea/R
• Intercept on the y axis, c = lnA