PChem Teaching Lab | Halogenation 3p2a

Composite Reactions & the Steady State Approximation

DECOMPOSITION OF AZOMETHANE

Hint

Given the equation

2AZO + AZO* → AZO + AZO* + C₂H₆ + N₂

it can be seen that

Species Number of molecules on the left hand side (lhs) of the equation Number of molecules on the right hand side (rhs) of the equation

AZO 2 1

AZO* 1 1

C₂H₆ 0 1

N₂ 0 1

Note: Species appearing on both sides of the equation can be cancelled appropriately, i.e. if 3 molecules of Species A appear on the lhs of the equation and 2 molecules of Species A appear on the rhs of the equation, then the 2 molecules on the rhs can be cancelled with two of the molecules on the lhs.

Overall Reaction

Summing the reactions in the proposed mechanism gives:

2AZO + AZO* → AZO + AZO* + C₂H₆ + N₂

On simplifying (by cancelling terms appearing on both sides of the equation)

The Overall Reaction (AZO → C₂H₆ + N₂) is not obtained
The Overall Reaction (AZO → C₂H₆ + N₂) is obtained

Species	Number of molecules on the left hand side (lhs) of the equation	Number of molecules on the right hand side (rhs) of the equation
AZO	2	1
AZO*	1	1
C₂H₆	0	1
N₂	0	1