Example of First order Reactions

Some common reactions which follow first order kinetics are listed below :

(1) Decomposition of N₂O₅ in CCl₄ solution. Nitrogen pentoxide in carbon tetrachloride solution decomposes to form oxygen gas,

The reaction is carried in an apparatus shown in Fig. 1.1. The progress of the reaction is monitored by measuring the volume of oxygen evolved from time to time.

If V_t be the volume of O₂ at any time t and V∞ the final volume of oxygen when the reaction is completed, the V_∞ is a measure of the initial concentration of N₂O₅ and (V_∞– V_t) is a measure of undecomposed N₂O₅ (a–x) remaining at time t. Thus,

On substituting values of V∞, (V_∞– V_t) at different time intervals, t, the value of k is found to be constant. Thus it is a reaction of the first order.