Chemical reaction engineering 2015

CHEMICAL REACTION ENGINEERING QUIZ

Q. 1 A catalyst slab of half thickness L (the width and length of the slab >>L) is used to conduct the first order reaction A → 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..........
Value of universal gas constant = 8.314 J/mol K.

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?

Zero order
Half order
First order
Second order

Q. 3 Which of the following can change if only the catalyst is changed for a reaction system?

Enthalpy of reaction
Activation energy
Free energy of the reaction
Equilibrium Constant

Q. 4 An irreversible, homogeneous reaction A → products, has the rate expression

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

0
1
1.5
2

Q. 5 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 of the following choices? Here, θ is dimensionless time.

Q. 6 An isothermal steady state mixed flow reactor (CSTR) of 1 m³ volume is used to carry out the first order liquid-phase reaction A → products. Fresh feed at a volumetric flow rate of Q containing reactant A at a concentration C_AO 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_v = 50% when the recycle ratio is increased to R=2, the new exit conversion (in percent) will be:

50.0
54.3
58.7
63.2

Q. 7 Consider two steady isothermal flow configurations shown schematically as case I and 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 V₁ 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 → products (order n) takes place in both cases, with a reactant concentration C_AO being fed into the first unit.

Choose the correct option

Q. 8.For a gas phase cracking reaction A → B+C at 3000C, the Gibbs free energy of the reaction at this temperature is ΔG0= -2750J/mo. The pressure is 1bar and the gas phase can be assumed to be ideal. The universal gas constant R = 8.314 J/mol.K. The fractional molar conversion of A at equilibrium is:

0.44
0.50
0.64
0.80