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1.	For the parallel reaction, A→B of order n1 and A→C of order n2, if B is the desired product, then which of the following reactor/ combination of reactors is used if n1 > n2?(a) CSTR(b) CSTR followed by Bubbling bed reactor(c) PFR(d) CSTR followed by PFRThis question was posed to me in a national level competition.I'm obligated to ask this question of Parallel Reactions Design topic in portion Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» CORRECT answer is (c) PFR Explanation: To maximise C\(_A^{n1-n2}\), PFR is used. If n1-n2 > 0, the AVERAGE concentration inside the REACTOR is maximum.

2.	For the parallel reaction, A→B, represented as (-rA) = k1CA^5and A→C represented as (-rA) = k2CA^3, theideal reactor preferred is ____(a) CSTR(b) CSTRs in parallel(c) CSTRs in series(d) PFRI had been asked this question in my homework.My question comes from Parallel Reactions Design in portion Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» The correct choice is (d) PFR Easy EXPLANATION: SELECTIVITY = \(\frac{k_1 C_A^5}{k_2 C_A^3}\) α CA^2 To INCREASE the yield of product, CA should be LARGE. Hence, PFR is used.

3.	The reaction yield is defined as the ratio of ____(a) Moles of reactant reacted to the moles of product formed(b) Moles of product formed to the moles of reactant reacted(c) Moles of desired product formed to the moles of undesired material formed(d) Moles of product formed to the moles of reactant fedThis question was addressed to me during an online exam.Query is from Parallel Reactions Design topic in chapter Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» The correct option is (b) Moles of product formed to the moles of reactant reacted The explanation: For a reaction, A → R, yield is \(\frac{C_R}{C_{A0}-C_A},\) Where, CA0 is the initial concentration of reactant CA is the FINAL concentration of reactant CR is the final concentration of product

4.	Selectivity in parallel reactions is defined as the ratio of___(a) Moles of desired product formed to the moles of undesired material formed(b) Moles of undesired product formed to the moles of desired material formed(c) Moles of product formed to the moles of reactant consumed(d) Moles of reactant consumed to the moles of product formedI had been asked this question in homework.My question is from Parallel Reactions Design in division Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» Right option is (a) MOLES of DESIRED product formed to the moles of undesired material formed The explanation: SELECTIVITY is defined for a parallel reaction. For a REACTANT A forming product B and an undesired product C, selectivity is the ratio of B to C.

5.	For the parallel reaction, A→B and A→C, if B is the desired product and the reaction A→B is of positive order n1 and C is the undesired product and the reaction A→C is of negative order n2, then increasing the concentration of A _____(a) Decreases desired product selectivity(b) Increases desired product selectivity(c) Initially increases and then decreases desired product selectivity(d) Does not affect desired product selectivityThe question was posed to me by my school principal while I was bunking the class.I would like to ask this question from Parallel Reactions Design in chapter Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» RIGHT CHOICE is (b) INCREASES desired product selectivity To elaborate: Selectivity = \(\FRAC{Rate \, of \, B \, formed}{Rate \, of \, C \, formed} \) Selectivity α\(\frac{C_A^{n1}}{C_A^{n2}}\) α C\(_A^{n1-n2}.\) As n2 is negative, increasing CA increases the selectivity of B.

6.	If the reactions A→B and A→C are represented as (-rA) = k1CA^3 and (-rA) = k2CA^6 of activation energies 130 and 150 J/ mol, then which of the following is the right selection of process parameters to increase selectivity of B?(a) CSTR, High temperature(b) PFR, High temperature(c) CSTR, Low temperature(d) PFR, Low temperatureThis question was posed to me by my college director while I was bunking the class.I'm obligated to ask this question of Parallel Reactions Design topic in portion Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» The correct option is (c) CSTR, Low temperature To EXPLAIN: Selectivity = \(\frac{k_1 C_A^3}{k_2 C_A^6} = \frac{k_1}{k_2}\) CA^-3 By Arrhenius equation, k = AE\(^\frac{-E_a}{RT} \) Since E1 < E2, temperature has to be DECREASED to INCREASE the yield of B.

7.	The autocatalyst in microbial fermentation reactions is:(a) Organic feed(b) Microbes(c) Enzyme(d) Product chemicalThe question was asked during an online interview.This key question is from Autocatalytic Reactions topic in division Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» Correct option is (b) Microbes To elaborate: The microbes ACT on the ORGANIC FEED to produce the product and more microbial cells. In microbial fermentation, the MICROBE which acts as the catalytic AGENT reproduces itself.

8.	If for the parallel reactions A→B and A→C, if the final concentration of B is 26 mol/ L and A converted is 36 mol/L, then the final concentration of C is ____(a) 15(b) 5(c) 6(d) 10This question was addressed to me in class test.This key question is from Parallel Reactions Design in portion Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» RIGHT OPTION is (d) 10 Easiest explanation: CA0 – CA = 36 CB = 26 CC = A CONVERTED – B formed CC = 10 mol/L.

9.	Which of the following reactors is used for carrying out autocatalytic reactions?(a) CSTR(b) PFR(c) Batch reactor(d) A combination of CSTR and PFR.This question was addressed to me in an interview.My query is from Autocatalytic Reactions topic in division Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» Right option is (d) A combination of CSTR and PFR. The explanation is: A combination of reactors is USED to OPTIMIZE the reactor volume. The reactors are arranged such that the required conversion is achieved. The volume should be LOW due to ECONOMIC considerations.

10.	The final concentration of product is related to the yield as ____(a) Final concentration = Yield × Reactant fed(b) Final concentration = Yield / Reactant fed(c) Final concentration = Yield × Reactant converted(d) Final concentration = Yield / Reactant fedI got this question in an internship interview.My question comes from Parallel Reactions Design in portion Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» Right option is (C) Final CONCENTRATION = Yield × Reactant CONVERTED For explanation I would say: Yield = \(\FRAC{Product \, formed}{Reactant \, converted} \) Product formed = Yield × Reactant converted.

11.	If the area under the curve of \(\frac{1}{-r_A} \) versus XA for a PFR used to carry out an autocatalytic reaction is 5\((\frac{m^3 s}{mol}),\) then the ratio of change in volume to molar feed rate is ____(a) 5(b) 10(c) 15(d) 20This question was posed to me during a job interview.Enquiry is from Autocatalytic Reactions topic in portion Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» Right choice is (b) 10 The best EXPLANATION: For a PFR, FA0dXA=(-rA)dV The AREA under the curve of \(\frac{1}{-r_A} \)VERSUS XA = \(\frac{DXA}{(-rA)} = \frac{dV}{F_{A0}}\) = 5.

12.	If A→B, (rB) = k1CA^2 and A→C, (rC) = k2CA^1, then the yield of C is ____(a) \(\frac{k_2}{k_2+k_1 C_A} \)(b) \(\frac{k_2}{k_2+k_1} \)(c) \(\frac{1}{k_2+k_1 C_A} \)(d) \(\frac{k_2}{k_1 C_A} \)I got this question in a job interview.The doubt is from Parallel Reactions Design topic in chapter Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» CORRECT CHOICE is (a) \(\FRAC{k_2}{k_2+k_1 C_A} \) Best explanation: Yield of C = \(\frac{k_2 C_A}{k_2+k_1 C_A^2} \) Yield of C = \(\frac{k_2}{k_2+k_1 C_A} \)

13.	Autocatalytic reactions are the ones in which ____(a) One of the products poisons the catalyst(b) There is no catalyst employed(c) Only one reactant is involved(d) One of the products catalyses the reactionThe question was posed to me in class test.Question is taken from Autocatalytic Reactions in portion Potpourri of Multiple Reactions, Design for Single & Parallel Reactions of Chemical Reaction Engineering
Answer» RIGHT option is (d) ONE of the products catalyses the reaction The EXPLANATION is: In autocatalytic REACTIONS, the reactant is CATALYZED by a product. One of the products is also a reactant.