DECOMPOSITION OF AZOMETHANE

Review

Overall Reaction	AZO → C2H6 + N2
Experimental Rate Law (at low [AZO])	+d[N2]/dt = ka[AZO]2
Proposed Mechanism
Overall Rate of Production of (Azomethane)*	d[AZO*]/dt = + k1[AZO]2 - k-1[AZO][AZO*] - k2[AZO*]
Overall Rate of Production of Nitrogen	d[N2]/dt = +k2[AZO*]
From the Steady State Approximation	[AZO*]SS = k1[AZO]2 / (k-1[AZO] + k2)

Eliminating [AZO*] from the Rate Expression for the Production of Nitrogen {+d[N₂]/dt}

Having obtained the Steady State Concentration of (Azomethane)*

[AZO*]_SS = k₁[AZO]² / (k_-1[AZO] + k₂)

(Note: The SS subscript is used to denote a Steady State term.)

this relationship can now be back-substituted into the expression for the overall rate of production of Nitrogen

d[N₂]/dt = +k₂[AZO*]

giving the result

d[N₂]/dt = k₁[AZO]² / (k_-1[AZO] + k₂)

d[N₂]/dt = k₂k₁[AZO]² / (k_-1[AZO] + k₂)

d[N₂]/dt = +k₂[AZO*]k₁[AZO]² / (k_-1[AZO] + k₂)