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1.	The value of the Peclet number for CSTR is ____(a) 1(b) 0(c) ∞(d) 2The question was posed to me in an internship interview.I need to ask this question from Non Ideal Reactors topic in chapter Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» The correct answer is (b) 0 To explain I WOULD say: CSTR is characterised by complete mixing and RECYCLING between the reactants and products. Hence, there is high diffusion of molecules WITHIN the REACTOR. As peclet number is inversely proportional to dispersion coefficient, PeCSTR = \(\frac{Lu}{∞}\) = 0.

2.	The exit age distribution as a function of time is ____(a) E = \(\frac{t^{N-1}}{τ^N}\frac{N^N}{(N-1)!}e^\frac{-tN}{τ}\)(b) E = \(\frac{t^{N-1}}{τ^N}\frac{N}{(N-1)!}e^\frac{-tN}{τ}\)(c) E = \(\frac{t^N}{τ^N}\frac{N^N}{(N-1)!}e^\frac{-tN}{τ}\)(d) E = \(\frac{t^{N-1}}{τ^2}\frac{N^N}{(N-1)!}e^\frac{-tN}{τ}\)I got this question in a national level competition.The doubt is from Tanks in Series Model topic in section Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» The correct option is (a) E = \(\FRAC{t^{N-1}}{τ^N}\frac{N^N}{(N-1)!}e^\frac{-tN}{τ}\) The best explanation: For N TANKS in series, the exit age DISTRIBUTION is, E = \(\frac{t^{N-1}}{τ^N}\frac{N^N}{(N-1)!}e^\frac{-tN}{τ}.\) The number of tanks in series, N = \(\frac{τ^2}{σ^2}. \)

3.	Which of the following represents Peclet number?(a) \(\frac{Lu}{D} \)(b) \(\frac{u}{D} \)(c) \(\frac{u}{DL} \)(d) \(\frac{D}{uL} \)I got this question in an interview for job.Question is taken from Non Ideal Reactors topic in division Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» RIGHT choice is (a) \(\frac{LU}{D} \) Easiest EXPLANATION: Peclet number ALSO defines the Dispersion model. It is the reciprocal of Dispersion number.

4.	The range of reactor peclet number for open tubes is ____(a) 10^6(b) 10^10(c) 10^2(d) 10^3The question was posed to me in unit test.The origin of the question is Non Ideal Reactors topic in section Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» Correct CHOICE is (a) 10^6 To elaborate: Peclet number for OPEN TUBES is GREATER than that in packed beds. In open tubes, there is no restriction to FLOW velocity.

5.	For a first order reaction, where k is the first order rate constant, the conversion for N tanks in series is obtained as ____(a) XA = 1-\(\frac{1}{(1+\frac{τk}{N})^N} \)(b) XA = 1+\(\frac{1}{(1+\frac{τk}{N})^N} \)(c) XA = \(\frac{1}{(1+\frac{τk}{N})^N} \)(d) XA = \(\frac{1}{(1+\frac{τk}{N})^N} \)– 1The question was posed to me by my school principal while I was bunking the class.I'm obligated to ask this question of Tanks in Series Model in chapter Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» Correct choice is (a) XA = 1-\(\FRAC{1}{(1+\frac{τk}{N})^N} \) The BEST explanation: For N tanks in series, the combination APPROACHES non – ideal PFR behaviour. The concentration in the N^th CSTR is GIVEN as CN = \(\frac{C_0}{(1+ τk)^N}.\frac{C_N}{C_0} = \frac{1}{(1+ τk)^N}.\) XA = 1 – \(\frac{C_N}{C_0}.\) For N – tanks, XA = 1-\(\frac{1}{(1+\frac{τk}{N})^N}. \)

6.	State true or false.The tank in series model depicts a non – ideal tubular reactor as a series of equal sized CSTRs.(a) The tank in series model depicts a non – ideal tubular reactor as a series of equal sized CSTRs.(b) True(c) FalseI had been asked this question during an online interview.Question is from Tanks in Series Model topic in chapter Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» Correct option is (a) The tank in SERIES model depicts a non – ideal TUBULAR reactor as a series of equal sized CSTRS. For explanation I WOULD say: A number of TANKS in series represent a PFR. Any CSTR behaves like a PFR if its volume is reduced. Infinite CSTRs are connected in series to approach PFR behaviour.

7.	The dispersion model accounts for ____(a) Deviation from ideal PFR(b) Modelling ideal CSTR(c) Combining batch and CSTR(d) CSTRs connected in parallelThe question was asked in a national level competition.This question is from Non Ideal Reactors in division Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» RIGHT choice is (a) DEVIATION from ideal PFR To elaborate: Dispersion MODEL involves a modification of the ideal PFR. It IMPOSES axial dispersion on plug FLOW.

8.	According to tanks in series model, the spread of the tracer curve is proportional to ____(a) Square of distance from the tracer origin(b) Square root of distance from the tracer origin(c) Cube of distance from the tracer origin(d) Inverse square of distance from the tracer originThe question was asked in a job interview.My question comes from Tanks in Series Model in chapter Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» Right choice is (B) Square root of DISTANCE from the tracer ORIGIN To explain: \(σ_{tracer \, curve}^2\) α Distance from point of origin Spread of the curve α \(\SQRT{Distance \, from \, origin}. \)

9.	State true or false.The tank in series model is a single parameter model.(a) The tank in series model is a single parameter model.(b) False(c) TrueI got this question in class test.My question is based upon Tanks in Series Model topic in division Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» Correct answer is (b) False Explanation: The tank in series MODEL is USED to represent non – ideal FLOW in PFR. It is a ONE parameter model and the parameter is the number of tanks.

10.	If τ = 5 s, first order rate constant, k = 0.25 sec^-1 and the number of tanks, N is 5, then the conversion is ____(a) 67.2%(b) 75%(c) 33%(d) 87.45%I had been asked this question in an interview.I need to ask this question from Tanks in Series Model in chapter Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» The correct option is (a) 67.2% For explanation: XA = 1-\(\FRAC{1}{(1+\frac{τk}{N})^N} \) 1-\(\frac{1}{(1+\frac{5×0.25}{5})^5}\) = 67.2%.

11.	If τ is the average residence time and σ^2 is the standard deviation, then the number of tanks necessary to model a real reactor as N ideal tanks in series is ____(a) N = \(\frac{\tau^2}{σ^2} \)(b) N = \(\frac{σ^2}{τ^2} \)(c) N = σ^2(d) N = \(\frac{1}{τ^2} \)The question was posed to me in semester exam.I need to ask this question from Tanks in Series Model in section Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» Right OPTION is (a) N = \(\FRAC{\tau^2}{σ^2} \) Best EXPLANATION: τ^2 = 1 and σ^2 = \(\frac{1}{N}.\) The standard deviation is obtained as, σ^2 = \(\int_0^∞\)(t-τ)^2E(t)DT.

12.	The range of dispersion number for PFR is ____(a) \(\frac{D}{uL}\) < 0.1(b) \(\frac{D}{uL}\) < 0.01(c) \(\frac{D}{uL}\) > 1(d) \(\frac{D}{uL}\) > 10The question was asked during a job interview.This question is from Non Ideal Reactors in section Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» The correct choice is (b) \(\FRAC{D}{uL}\) < 0.01 The best explanation: For PFR, \(\frac{D}{uL}\) < 0.01. Due to NEGLIGIBLE dispersion in PFR, \(\frac{D}{uL}\) nearly APPROACHES 0.

13.	If τ^2 = 100 and σ^2 = 10, the number of tanks necessary to model a real reactor as N ideal tanks in series is ____(a) 1(b) 10(c) 5(d) 100I got this question in a national level competition.My question comes from Tanks in Series Model in section Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» CORRECT OPTION is (B) 10 Best explanation: N = \(\frac{τ^2}{σ^2} \) N = \(\frac{100}{10}\) = 10.

14.	Which of the following correctly represents the Damkohler number for a first order reaction? (Where, τ is the space time)(a) k(b) τ(c) \(\frac{1}{kτ}\)(d) k τThe question was posed to me in examination.My question comes from Tanks in Series Model in division Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» CORRECT option is (d) k τ To elaborate: Damkohler number is the PRODUCT of first order rate constant and SPACE TIME. It is the measure of the degree of completion of REACTION.

15.	The dispersion model is a ____(a) Two parameter model(b) One parameter model(c) No parameter model(d) Three parameter modelThis question was addressed to me in an interview for job.Query is from Non Ideal Reactors in division Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» Right answer is (b) ONE parameter model To explain: Dispersion model is a one parameter model. The parameter MODELLING the non – ideal CONDITION is the dispersion COEFFICIENT.

16.	The value of the Dispersion coefficient for plug flow is ____(a) 1(b) 0(c) ∞(d) 2I got this question in an online quiz.This question is from Non Ideal Reactors topic in chapter Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» RIGHT CHOICE is (b) 0 For explanation I would SAY: There is no AXIAL MIXING in a PFR. Hence, the dispersion of the fluid in the longitudinal direction is assumed to be zero.

17.	If D is the fluid dispersion coefficient, L is the length of spread of tracer and u is the fluid velocity, thenwhich of the following represents Dispersion number?(a) \(\frac{L}{uD}\)(b) \(\frac{L}{D}\)(c) \(\frac{D}{uL}\)(d) \(\frac{Lu}{D}\)I got this question by my college director while I was bunking the class.I'd like to ask this question from Non Ideal Reactors topic in chapter Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» Right OPTION is (c) \(\FRAC{D}{uL}\) Easiest explanation: DISPERSION number is a dimensionless group characterizing spread in the entire reactor vessel. The value of D determines the spread.

18.	There are 5 tanks connected in series. If the average residence time is 5 sec, first order rate constant is 0.5 sec^-1, the initial concentration is 5\(\frac{mol}{m^3},\) then the conversion at the exit of 5^th reactor in (\(\frac{mol}{m^3}\)) is ____(a) 0.34(b) 0.51(c) 0.65(d) 0.81This question was posed to me in quiz.This interesting question is from Tanks in Series Model in portion Compartment Models, Models for Non Ideal Reactors of Chemical Reaction Engineering
Answer» The correct answer is (C) 0.65 The BEST EXPLANATION: CN = C0 \(\frac{1}{(1+\frac{τk}{N})^N} \) CN = 5×\(\frac{1}{(1+\frac{5×0.5}{5})^5}\) CN = 0.65\(\frac{mol}{m^3}. \)