Example 3.5

Example . Let us consider a typical first order gas phase reaction A(g) ® B(g) + C(g) Let p i be the initial pressure of A and p t the total pressure at time ‘ t ’. Integrated rate equation for such a reaction can be derived as Total pressure p t = p A + p B + p C (pressure units) p A , p B and p C are the partial pressures of A, B and C, respectively. If x atm be the decrease in pressure of A at time t and one mole each of B and C is being formed, the increase in pressure of B and C will also be x atm each. A(g) ® B(g) + C(g) At t = p i atm atm atm At time t ( p i –x) atm x atm x atm where, p i is the initial pressure at time t = . p t = ( p i – x) + x + x = p i + x x = ( p t - p i ) where, p A = p i – x = p i – ( p t – p i ) = p i – p t k = i A log p           ( . )   i i . log The following data were obtained during the first order thermal decomposition of N O (g) at constant volume: