279) The rate constant of a zero order reaction is 0.2 mol dm⁻³hr⁻¹ of the concentration of the reactant after 30 minutes is 0.05 mol dm⁻³ then its initial concentration would be:

280) Collision theory is applicable to :

281) The half life of a second order reaction is:

282) 16.0 gm of a radioactive substance is reduced to 0.50 g after 2 hours. Then the half life of the radioactive substance is:

283) The decomposition of N₂O into N₂ and O follows the second order kinetics with K = ( 5 x 10 ¹¹ mol⁻¹sec⁻¹) e ^{−29000K⁄T} then, the energy of activation of this reaction is: