Consider the gaseous reaction, A(g) → 3B(g). The initial pressure of ‘A’ is ‘po' mm and total pressure after time ‘t’ is ‘pt’ mm. If the reaction follows first order kinetics, the correct expression for rate constant (K) is

Total pressure after time ‘t’ = (po - x + 3x)Total pressure(pt) after time ‘t’ = po  + 2xx=pt−po2  initial pressure of ‘A’ = popressure of ‘A’ after time ‘t’ = po−pt−po2pressure of ‘A’ after time ‘t’ = 3po−pt2k=2.303tlog2po3po−pt