What is the value of the activation energy?

If a reaction has k=3.0 x 10^4 s-1 at 25°C and an activation energy of 100.0 kJ/mol, what will the value of k?

• If a reaction has k= 3.0 x 10^-4 s^-1 at 25°C and an activation energy of 100.0 kJ/mol, what will the value of k be at 50°C?

• Answer:

  You have to use the Arrhenius equation twice: k = A e^(-E/RT) where, k = rate constant at Temperature T A = Arrhenius constant E = Activation energy = 100 * 10^3 J/mol R = Universal Gas constant = 8.314 J/(K mol) First use this equation for T = 25 deg C (= 298 K), to find the value of A A = k/e^(-E/RT) = 3 * 10^(-4)/e^{-100 * 10^3/(8.314*298)} Now insert this value of A in the following equation to find out k at T = 50 deg C (= 323 K) k = A e^{-100 * 10^3/(8.314*323)} k = 6.82 * 10^(-3) s^(-1) (Well, I haven't shown the calculations here as I've used scientific calculator to compute this value)