For a homogeneous gaseous reaction, A B C D, -> in the initial pressure was P0 while pressure after time t was P. Expression for rate constant K in terms of P0, P and t is: (a) 2P 2.303 K log t 3P P (b) 4P 2.303 K log t 2P P (c) 3P 2.303 K log t P P

Initial pressure = P0 From reaction, Total pressure at time t =P = P0 –x+x+x+x=P0 + 2x 2x = P – P0 0 0 0 0 0 0 0 0 0 P P x 2 P P 3P P P x P 2 2 P 2P P x 3P P The expression for rate constant is 0 0 2P 2.303 K log t 3P P Some Important First Order Reactions