Chemical Reaction Engineering GATE-2015

Q 1. Which of the following can change if only the catalyst is changed for a reaction system?

A) Enthalpy of the reaction
B) Activation energy
C) Free energy of the reaction
D) Equilibrium constant

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Q 2. For which reaction order, the half-life of the reactant is half of the full lifetime (time for 100 % conversion) of the reactant?

A) Zero order
B) Half order
C) First order
D) Second order

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Q 3. An irreversible, homogenous reaction A \rightarrow Products, has the expression:

Rate=\frac{2{C_A}^2+0.1C_A}{1+50C_A}

Where C_A is the concentration of A. C_A varies in the range of 0.5 – 50 mol/m³. For very high concentrations of A, the reaction order tends to:

A) 0
B) 1
C) 1.5
D) 2

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Q 4. Consider two steady isothermal flow configurations shown schematically in Case I and Case II below. In Case-I, a CSTR of volume V₁ is followed by a PFR of volume V₂, while in Case-II a PFR of Volume V₂ is followed by a CSTR of volume V₁. In each case, a volumetric flow rate Q of liquid reactant is flowing through the two units in series. An irreversible reaction A \rightarrow products (order n) takes place in both cases, with a reactant concentration C_A0 being fed into the first unit.

Choose the correct option:

A) \frac{C_{A_f}^I}{C_{A_f}^{II}}>1\;for\;n=1
B) \frac{C_{A_f}^I}{C_{A_f}^{II}}=1\;for\;n=1
C) \frac{C_{A_f}^I}{C_{A_f}^{II}}≺1\;for\;n=1
D) \frac{C_{A_f}^I}{C_{A_f}^{II}}=1\;for\;n>0

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Q 5. A catalyst slab of half-thickness L (the width and length of the slab >> L) is used to conduct the first-order reaction A \rightarrow B. At 450 K, the Thiele modulus for this system is 0.5. The activation energy for the first order rate constant is 100 kJ/mol. The effective diffusivity of the reactant in the slab can be assumed to be independent of temperature, and external mass transfer resistance can be neglected. If the temperature of the reaction is increased to 470 K, then the effectiveness factor at 470 K (up to two decimal places) will be ______________. The value of the universal gas constant = 8.314 J/mol.K.

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Q 6. The impulse response to a tracer pulse experiment for a flow reactor is given below:

In the above figure, C is the exit tracer concentration. The corresponding E or E_θ (normalized E) curve is correctly represented by which following choices? Here, θ is dimensionless time.

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Q 7. An isothermal steady state mixed flow reactor (CSTR) of 1 m³ volume is used to carry out the first order liquid-phase reaction A \rightarrow products. Fresh feed at a volumetric flow rate of Q containing reactant A at a concentration C_A0 mixes with the recycle stream at a volumetric flow rate RQ as shown in the figure below

It is observed that when the recycle ratio R = 0.5, the exit conversion X_Af = 50%. When the recycle, the ratio is increased to R = 2, the new exit conversion (in percent) will be:

A) 50.0
B) 54.3
C) 58.7
D) 63.2

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