The gas phase decomposition of azomethane to give ethane and nitrogen takes place according to the following sequence of elementary reactions.

(CH${_3}){_2}$N${_2}$ + (CH${_3}){_2}$N${_2}$ $\rightarrow ^{K_1}$ (CH${_3}){_2}$N${_2}$ + [(CH${_3}){_2}$N${_2}$]*

[(CH${_3}){_2}$N${_2}$]* + (CH${_3}){_2}$N${_2}$ $\rightarrow^{K_2}$ (CH${_3}){_2}$N${_2}$ + (CH${_3}){_2}$N${_2}$

[(CH${_3}){_2}$N${_2}$]* $\rightarrow^{K_2}$ C${_2}H{_6}$ + N${_2}$

Using the pseudo-steady-state-approximation for [(CH${_3}){_2}$N${_2}$]*, the order with respect to azomethane in the rate expression for the formation of ethane, in the limit of high concentrations of a azomethane, is $\_\_\_\_\_\_$