The gas-phase oxidation of nitric oxide (nitrogen monoxide, NO) has an overall r

Question

The gas-phase oxidation of nitric oxide (nitrogen monoxide, NO) has an overall reaction written as: 2 NO(g) + O2(g) 2 NO2(g). The reaction has an overall third order with a rate law rate kNOJIO:]. The reaction goes through the following elementary steps: NO + NOF.AN 202 (a) Derive the above rate law for NO2 formation using the steady-state approximation; (b) Assuming all the rate constants obeys Arrhenius equation, drive a relationship that relates the "apparent" activation energy in ke to the activation energies of the elementary steps.

Explanation / Answer

given NO+NO<---->N2O2 (1)with forward rate constant of Ka and backward reaction rate constant of Ka'

N2O2+O2-------->2NO2 (2), rate constant is Kb

rate of formation of NO2= Kb[N2O2][O2] (3)

N2O2 is the intermediate whose net rate is zero.

This is formed from reaction- 1 and decmposed through backward reaction and decomposed through reaction-2

it being intermediate, its net rate =0

net rate= Ka[NO[NO]- Ka' [N2O2]-Kb[N2O2][O2]=0

[N2O2] = Ka[NO]2/ ( Ka'+ Kb[O2] (4)

Substituting the value of [N2O2] in Eq.3 gives

rate of formation of NO2 =KbKa[NO]2 [O2]/ { Ka'+ Kb[O2]}

when Ka>>Kb[O2], the rate becomes = KaKb[NO]2[O2]/Ka'= Kr [NO]2 [O2], where Kr= KaKb/Ka'

Ka= rate constant = Kao*e(-Ea0/RT), as per Arhenius equation, where Ea0= activation energy of reaction-1

Ka'= Kao'e(-Ea0'/RT), Eao'= activation energy for reverse reaction of -1

Kb= rate constant =kbo*e(-Eab/RT), Ea2= activation energy of reaction -2

Hence KaKa/Ka' = Kao*Kboe(-Eao/RT-Eab/RT)/ Kao' e(-Eao'/RT)= (Kao*Kbo/Kao')e{Ea0'/RT-(Eao/RT+Eab/RT)}

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

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