Question

The reaction: 2H2O2(l)---> 2H2O(g)+O2(g) is the 1st order on H2O2. The reaction is slow in the absence of catalyst. With a small amount of Fe3+ the reaction is accelerated. If initially 0.437M of H2O2 is added to the solution, the reaction proceeds with a half-time 17.3 min at 300K, what is the concentration of H2O2 in solution after 10 min? same experiment if run at 350K has a half-life of 10 min, what is the activation energy for the catalyzed reaction?

Answer 1

first order kinetics

k = (1/t)ln(a0/a)

k = rate constant = 0.0693/t1/2 = 0.0693/17.3 = 0.004 min-1

t = time taken = 10 min

a0 = initial concentration of H2O2 = 0.437 M

a = final concentration of h2o2 = ?

0.004 = (1/10)ln(0.437/a)

a = final concentration of h2o2 = 0.42 M

at 350 k,

K2 = rate constant = 0.0693/t1/2 = 0.0693/10 = 0.00693 min-1

Arrhenius equation

ln(k2/k1) = Ea/R[1/T1 - 1/T2]

Ea = activation energy = ?

K1 = 0.004 min-1 , T1 = 300 K

K2 = 0.00693 min-1 , T2 = 350 K

ln(0.00693/0.004) = (x/8.314)((1/300)-(1/350))

Ea = 9.6 kj/mol