Test: Steady State Approximation in Reaction Mechanisms - Chemistry MCQ

Reaction of COCl. with Cl₂ is the slow reaction. Hence, it is the rate determining step.

The rate expression for decomposition of azomethane is:

Where, k₁, k₂ and k₃ are rate constants of the 3 intermediate reactions involved in azomethane formation.
At low concentration, k₂ C_Azo << k₃
Hence, r_N2=k₁CAzo₂.

In the first step, 2 molecules of NO form N₂O₂. Further oxidation of N₂O₂ is the slowest step and it is the rate determining step.

Rate determining step is the slowest of all the reaction steps. The rate determining step is important in deriving the rate equation of a chemical reaction.

In the slow step, iodine decomposes to give 2[I]. In the consequent step, hydrogen reacts with 2[I] to give hydrogen iodide.

The rate of decomposition of ozone is:
-rO₃= k[O₃]²[O2]^-1
Order = 2-1 = 1

The steady-state approximation is a method used to derive the rate expression. It is based on the assumption that one intermediate in the reaction mechanism is consumed as fast as it is generated.

For a zero order reaction,

A forms two products: B and C. The concentration of A decreases as the reaction progresses.

The rate of N₂O₅ decomposition is given by, r = k[N₂O₅].
Hence, the reaction follows first order.

The rate expression is, r_N2 = 
At low concentrations of N₂O, kNO₂ << 1 and the reactions follows second order. At high concentrations of N₂O, kNO₂ >> 1 and the reaction follows first order.