The Rate Constant and the Arrhenius Equation

• The Arrhenius equation links the rate constant, activation enthalpy and temperature

• k = Ae^-Ea/RT (given on the data sheet)

• k = rate constant

• Ea = activation energy (Jmol^-1)

• T = temperature (K)

• R = gas constant (given on data sheet)

• A = the pre-exponential factor (includes factors such as frequency of collisions, orientation of collisions)

• e = constant (on calculator)

• As Ea increases, k decreases

• As T increases, k increases

Finding Ea or A from the Arrhenius equation

• The Arrhenius equation can be rearranged

• lnk = -Ea/RT + lnA (given on the data sheet)

• Plotting a graph of lnk against 1/T gives a straight line.

• -Ea/R is the gradient and lnA is the y intercept