Question

Consider the following reaction on acetone (CH3COCH3), the mechanism is believed to involve four elementary steps: CH3COCH; 4+ CH3 + CH3CO CH3 + CH3COCH; CH4 + CH3COCH, CH;COCH2 _ky → CH3 + CH2CO CH3 + CH3COCH, ko > CH3COCZH (a) Write down an expression for the rate of disappearance of CH3COCHz. (3 marks) Assume kz >> k[CH3), apply the steady-state approximation and work out an expression for (CH3) in term of kį, kz, kz and ke. Show all of your work. (6 marks) (C) Deduce the rate law for [CH3COCH3]. (3 marks)

Answer 1

I am given above all three answers please read carefully.

CCCCCCCCCCC Here, the given rexn's involve four elementary steps: (1) CH₃ COCH Ki City + Cty co rate= ((Hz Cochy] = ki [CH₂ COCHz] I (ii) CH₂ + CHz Cocthy Ki CH4 + CH ₂ CO CH2 : rate = K2 [che] [chy cocky] (ii) CH₂ CO CHA K CH₂ + CH₂ CO rate= K₂ [CH₂ CO CH₂] CH₃ + CH ₂ CO CH₂ Kn CH₃ CO Caths rate = Ku [che] [chy Cochz] Ang @ as step(i), 2) ] [Chacoche] = [CH] [chtcom Hangs step (ii); -1 [CH₂ CO CH₂ = 1 [Chur - TCHCOCH edt. 03.07 CO Hence, we rate of as shown derive an expressions for the disapperance of CH₂ CO CH₂ in step no. (i) and (ii).

Ans (6) 2 Assume kz » Ky [CH₃) apply the Steady -State approximation and we are work out an expression for [CH3] in term of ki, K2, kz and ku. SASILDIIIT!) So, - CcHg] =0 : got D dts . - 1 [Intermediate] =0 at By using all the steps (i) (i), (iii) 4 (iv) Ki [chy cochz] - Kz [che] [chy cochz] + K3 [CMg Coche] - Ky [CH₂] [CH₂ CO CH₂] =0 take an assume Kg >> Kuj [CH3] , (k, - Kq (CH3)) [CH₂ COCHy] = (K4 [CM3] - Kg) [CH ₂ CO CHz] Con so, neglecting Kq (CH ₃ we get Ki [CH, CO CHE] - Kz [chg] [chycocug) -K3 [CH3 Coche] 2. Ky - Kż (cha] - Ky [CH, Coche] [CH₂ CO CH₂ K2 (Mg] =- [It, Cock) + K:] 99 CH3 COCH3] Ky [cly] = Kg [Chy. Cochy] + R, [chy coch,) (си, со си) .. [CH] = R3 [cHz Coche] + K, [CH, COCHE] K₂ [CH₃COCH ₃] 000 WIN

using [CHg] in egastep (iv) we get, rate = Ku [CH3] [CH3CO CH2] rate = kq [K3 [CH₃ Cochz] + Ki [Cth CO CH₂] [CH₂ CO CH₂ K, [си, сосн) Ans (C) for steps, (ii) the rate law for [CH₂ COCHz] rate=k, (CH ₂ CO CH3] = rei rate = K₂ [Cr23] [CH₃CO CH₂) = der UUUUUCccccccc r = K [CH₂ CO CH3] Ez . Kz CC Coche] [che]