The rate constant for the decomposition of acetaldehyde, CH3CHO, to methane, CH4, and carbon monoxide, CO, in the gas phase is 1.1 × 10−2 L/mol/s at 703 K and 4.95 L/mol/s at 865 K. Determine the activation energy for this decomposition.
Solution :-
Rate constant K1 =1.1*10^-2 L/mol/s
Temperature T1 = 703 K
Rate constant K2 = 4.95 L /mol/s
Temperature T2 = 865 K
Activation energy Ea= ?
Using the Arrhenius equation we can calculate the activation energy as follows
ln[K2/K1] = Ea/R [ (1/T1)-(1/T2)]
lets put the values in the formula (R= 8.314 J per K mol )
ln[4.95/1.1*10^-2]= Ea/ 8.314 J per K mol [ (1/703)-(1/865)]
6.109 = (Ea/8.314 J per mol K) * 0.0002664
Ea = 6.109 * 8.314 J per K mol / 0.0002664
Ea = 190654 J per mol
190654 J per mol * 1 kJ / 1000 J = 190.6 kJ per mol
Therefore activation energy is 190.6 kJ per mol
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