Exercise 5 | Chemical Kinetics: Mechanisms

The rate of an elementary reaction has been studied as a function of temperature.

The following data were obtained for the rate constant:

Exp 1: T = 300K; k = 6.47 mol.L-1.s-1

Exp 2: T = 500K; k = 2.84 x 104 mol.L-1.s-1

Exp 3: T = 700K; k = 1.03 x 106 mol.L-1.s-1

 

Calculate the activation energy for the reaction.

Arrhenius equation:

k = Ae-Ea/RT

 

k2 / k1 = Ae-Ea/RT2 / Ae-Ea/RT1

 k2 / k1 = e-Ea/RT2 + Ea/RT1

 ln (k2 / k1) = EaR 1T1 - 1T2

⇒ Ea = ln 2.84 × 1046.47 × 8.3141300 - 1500 = 5.23 x 104 J = 52.3 kJ