Chemical Reaction Engineering GATE-2013

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Q 1: The exit age distribution for a reactor is given by E(t) = δ(t – 4), where t is in seconds. A first-order liquid phase reaction (k = 0.25 s-1) is carried out in this reactor under steady state and isothermal conditions. The mean conversion of the reactant at the exit of the reactor, up to 2 digits after the decimal point, is ______.

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Q 2: An isothermal liquid phase zero order reaction A → B (k = 0.5 mol/m3-s) is carried out in a batch reactor. The initial concentration of A is 2 mol/m3. At 3 seconds from the start of the reaction, the concentration of A in mol/m3 is __________.

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Q 3: The overall rates of an isothermal catalytic reaction using spherical catalyst particles of diameters 1 mm and 2 mm are rA1 and rA2 (in mol (kg-catalyst)-1 h-1), respectively. The other physical properties of the catalyst particles are identical. If pore diffusion resistance is very high, the ratio rA2/rA1 is __________.

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Q 4: The gas phase decomposition of azomethane to give ethane and nitrogen takes place according to the following sequence of elementary reactions.

(CH_3)_2N_2+(CH_3)_2N_2\xrightarrow{k_1}(CH_3)_2N_2+\lbrack(CH_3)_2N_2\rbrack^\ast \left[(CH_3)_2N_2\right]^\ast+(CH_3)_2N_2\xrightarrow{k_2}(CH_3)_2N_2+(CH_3)_2N_2 \left[(CH_3)_2N_2\right]{}^\ast\xrightarrow{k_3}C_2H_3+N_2

Using the pseudo-steady-state-approximation for [(CH3)2N2]*, the order with respect to azomethane in the rate expression for the formation of ethane, in the limit of high concentrations of azomethane, is ___________.

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Q 5: A first-order liquid phase reaction is carried out isothermally at a steady state in a CSTR and 90 % conversion is attained. With the same inlet conditions and for the same overall conversion, if the CSTR is replaced by two smaller and identical isothermal CSTRs in series, the % reduction in total volume, to the nearest integer, is __________.

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Common data for Q 6 & 7:

Liquid reactant A decomposes as follows

A\rightarrow R\;\;r_R=k_1C_A^2\;\;\;k_1=0.5m^3/mol‐s A\rightarrow S\;\;r_S=k_2C_A\;\;k_2=1s^{-1}

An aqueous feed of composition CA0 = 30 mol/m3, CR0 = 2 mol/m3, and CS0= 1 mol/m3 enters a CSTR in which the above reactions occur. Assume isothermal and steady-state conditions.

Q 6: If the conversion of A is 80 %, the concentration of R in the exit stream in mol/m3, to the nearest integer, is _________.

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Q 7: What is the % conversion of A, to the nearest integer, so that the concentration of S in the exit stream is 11.8 mol/m3? _________

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