Chemical Reaction Engineering GATE-1998

Q 1: For reaction P + Q → R + S, the molar rate of consumption of P is

A) double of that of Q
B) same as that of Q
C) half of that of Q
D) 2/3 of that of Q

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Q 2: Molecularity of an elementary reaction P + Q → R + S is

A) 1
B) 2
C) 3
D) 4

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Q 3: Second-order consecutive irreversible reactions $A\xrightarrow{k_1}B\xrightarrow{k_2}C$ were carried out in a constant volume isothermal batch reactor with different initial feed compositions. The reactor temperature was the same in all the cases. In experiments where the ratio of the concentration of B to that of A in the initial feed was less than 0 5, the concentration of B increased first, reached a maximum, and then declined with time. However, for all experiments where this concentration ratio was 0.5 or above, the concentration of B decreased monotonically with time right from the beginning. What is the ratio of the two rate constants (k₁/k₂)?

A) 1/4
B) 1/2
C) 2
D) 4

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Q 3: A spherical porous catalyst particle of radius R is subjected to reactant A which reacts to form B by a zero-order surface reaction A → B. Film mass transfer resistance is negligible and pore diffusion of A is rate controlling. The effectiveness factor of the catalyst is reported as 7/8. Which of the following statements is true?

A) Inner catalyst core of radius R/8 does not participate in reaction
B) Inner catalyst core of radius R/2 does not participate in reaction
C) Inner catalyst core of radius 7R/8 does not participate in reaction
D) Effectiveness factor for a zero-order reaction cannot be 7/8 as it must always be 1

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Q 5: A liquid phase, first order, reversible reaction A → B is carried out in a continuous stirred tank reactor (CSTR). The molar densities of A and B are the same. Other things (such as space-time, flow rate, and temperature) remain the same, a feed of pure A to the reactor results in a 40 % conversion of A, while a feed of pure B results in a 50 % conversion of B. Estimate the reaction equilibrium constant. Assume steady state operation in both cases.

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Q 6: Steady state plug flow reactor (PFR) data for the isothermal irreversible reaction A → B is as shown in the table.

	Concentration of A (kmol/m3)
	In Feed	In Product
Case-I	1	0.5
Case-II	2	0.555

Reactor space-time was 10 seconds in both cases. Other things such as feed and product density, reactor temperature, etc. are the same in both cases. If the reaction is known to be of non-zero integer order, find the reaction order and the rate constant.

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