In: Chemistry
Determine the activation energy in kJ/mol for a first order reaction if its specific rate constant 8.30e-05 s-1 at 350.0 K and 3.25e+01 s-1 at 560.0 K.
Ea = ______ kJ/mol
According to Arrhenius Equation , K = A e -Ea / RT
Where
K = rate constant
T = temperature
R = gas constant = 8.314 J/mol-K
Ea = activation energy
A = Frequency factor (constant)
Rate constant, K = A e - Ea / RT
log K = log A - ( Ea / 2.303RT ) ---(1)
If we take rate constants at two different temperatures, then
log K = log A - ( Ea / 2.303RT ) --- (2)
& log K' = log A - (Ea / 2.303RT’) ---- (3)
Eq (3 ) - Eq ( 2 ) gives
log ( K' / K ) = ( Ea / 2.303 R ) x [ ( 1/ T ) - ( 1 / T' ) ]
Ea = [(2.303R x T x T’) / (T’ - T)] x log (K’ / K)
Given K = 8.30x10-5 s-1
K' = 3.25x10+1 s-1
T = 350.0 K
T' = 560.0K
Plug the values we get Ea = 99.9x103 J/mol
= 99.9 kJ/mol