Use the steady-state approximation to derive the rate equation 2NO2 + Cl2 ? 2NO2

Question

Use the steady-state approximation to derive the rate equation

            2NO2 + Cl2 ? 2NO2Cl (overall reaction)

            Mechanism

                                                k1

            Step 1     NO2 + Cl2  ? NO2Cl + Cl         

                                                   k-1

                                                  k2                     

            Step 2        NO2 + Cl   ?   NO2Cl      

Explanation / Answer

Step 2 is the slow step so it gives the rate law:

d[NO2Cl]/dT = k2[NO2][Cl]/[NO2Cl] ............(1)

[Cl] is an unstable species. Applying steady state approximation to it.

d[Cl]/dT = 0

k1[NO2]2[Cl2] - k-1[NO2Cl][Cl] = 0

k1[NO2]2[Cl2] = k-1[NO2Cl][Cl]

[Cl] = k1/k-1 [NO2][Cl2] / [NO2Cl]

Putting value to [Cl] in (1)

d[NO2Cl]/dT = k2k1/k-1[NO2]3[Cl2] / [NO2Cl]      Overall rate equation

Related Questions

Navigate

• Browse (All)
• Browse U
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.