Gaseous cyclobutene isomerises to butadiene in a first order process which has a 'k' value of 3.3 $$ \times $$ 10^-4 s^-1 at 153°C. The time in minutes it takes for the isomerization to proceed 40% to completion at this temperature is ______.
(Rounded off to the nearest integer)

The rate of a reaction decreased by 3.555 times when the temperature was changed from 40^oC to 30^oC. The activation energy (in kJ mol^–1) of the reaction is _______.

Take; R = 8.314 J mol^–1 K^–1 ln 3.555 = 1.268

The number of molecules with energy greater than the threshold energy for a reaction increases five fold by a rise of temperature from 27^oC to 42^oC. Its energy of activation in J/mol is _____.
(Take ln 5 = 1.6094; R = 8.314 J mol^–1 K^–1)

If 75% of a first order reaction was completed in 90 minutes, 60% of the same reaction would be completed in approximately (in minutes) _______.

(Take : log 2 = 0.30; log 2.5 = 0.40)