Chapter 5 - Ideal Reactors for Single Reaction

Question 1

in this reactor, the reactants are initially charged into
a container, are well mixed, and are left to react for a certain period

Answer 1

batch reactor

Question 2

this reactor has an unsteady-state operation where composition
changes with time; however, at any instant the composition throughout the
reactor is uniform.

Answer 2

batch reactor

Question 3

in this reactor, characterized by the fact that the flow of fluid
through the reactor is orderly with no element of fluid overtaking or mixing with
any other element ahead or behind

Answer 3

plug flow reactor

Question 4

in this reactor, there may be lateral mixing of
fluid but there must be no mixing or diffusion along the flow path

Answer 4

plug flow reactor

Question 5

necessary and sufficient condition for ______ reactor is for the
residence time in the reactor to be the same for all elements of fluid

Answer 5

plug flow

Question 6

a reactor in which the contents are well stirred and uniform throughout

Answer 6

mixed flow reactor

Question 7

in this reactor, the exit stream from this reactor has the same composition as the fluid within
the reactor

Answer 7

mixed flow reactor

Question 8

refers to the volume of fluid in the reactor

Answer 8

V, reactor volume

Question 9

in this reactor, there is no fluid enters or leaves the reaction mixture
during reaction

Answer 9

batch reactor

Question 10

the natural performance measure for a batch reactor

Answer 10

reaction time, t

Question 11

time required to process one
reactor volume of feed measured
at specified conditions

Answer 11

space time

Question 12

number of reactor volumes of
feed at specified conditions which
can be treated in unit time

Answer 12

space velocity

Question 13

in this reactor, the composition of the fluid varies from point to point
along a flow path

Answer 13

plug flow reactor

Question 14

in PFR, _____ is constant but _____ is certainly dependent on the concentration or convesion of materials

Answer 14

Fao, rA

Question 15

in ___ rA varies while in ___ rA is constant

Answer 15

PFR, MFR

Question 16

for systems of changing density, it is more convenient to use ___________

Answer 16

conversions

Question 17

when the density is constant, Ea = ?

Answer 17

0

Question 18

for systems of constant density (constant-volume batch and constant density plug flow), the performance equation are ______ and equations can be used interchangeably.

Answer 18

identical

Question 19

for systems of changing density, there is (direct, no direct) correspondence between the batch and plug flow ewuations

Answer 19

no direct

Question 20

it is applicable to an even number of uniformly spaced intervals on the Xa axis

Answer 20

simpson’s rule

Question 21

in PFR, as space time increases, concentration of reactant ______

Answer 21

decreases

Question 22

in batch reactor, as reaction time increases, concentration of reactant __________

Answer 22

decreases

Question 23

reactors whose properties of the system do not change with time

Answer 23

steady state reactor

Question 24

reactors whose properties of the system changes with time and rate of reaction decreases with time

Answer 24

unsteady state reactor

Question 25

partially batch and partially continuous; offers good control of reaction speed because the reaction proceeds as reactants are added.

Answer 25

semi batch reactors

Question 26

which achieves higher conversion among the flow reactors for identical conditions?

Answer 26

for identical conditions, i.e for some reactor volume conversion achieved in PFR is higher than in MFR

Question 27

in this reactor, rate of reaction is independent of time and dependent on position or distance

Answer 27

PFR

Question 28

in this reactor, rate of reaction is independent of position and dependent on concentration of reactants

Answer 28

MFR

Question 29

reactor that is most suitable for very high pressure gas phase reaction

Answer 29

tubular flow reactor

Question 30

reactor that is most suitable for isothermal operation

Answer 30

back-mix reactor

Question 31

reactor for reactions where the reaction rate is fairly to extremely high, for large scale production and for good quality control

Answer 31

PFR

Question 32

a large CSTR, small CSTR and PFR of fixed volume are available. In general, how would you arrange them for getting maximum conversion for reactions of order >1 and <1. Why

Answer 32

For n>1 arrangement is PFR followed by small CSTR followed by large CSTR to maintain the reactant concentration as high as possible. For n<1 arrangement is large CSTR followed by small CSTR followed by PFR. For n=1 arrangement for first order reaction sequencing does not affect conversion. It can be either PFR followed by MFR or MFR followed by PFR.

Question 33

reactor used to increase conversion rate by dividing the product stream and a part returned to the reactor as recycle

Answer 33

recycle reactor

Question 34

provides means for obtaining various degree of back mixing

Answer 34

recycling

Question 35

ratio of the volume fluid returned to the reactor entrance to the volume of fluid leaving the system or reactor

Answer 35

recycle ratio

Question 36

recycle ratio can be made to vary from _____ to infinity

Answer 36

zero

Question 37

as the recycle ratio is raised, the behavior shifts from ___ (R = 0) to ______ (R = infinity)

Answer 37

PFR, MFR

Question 38

when will the recycle reactor behave like a CSTR?

Answer 38

when the recycle ratio ‘R’ becomes or tends to infinity (R=infinity), the recycle reactor behaves like a CSTR

Question 39

what do you mean by optimum recycle operation?

Answer 39

when material is to be processed to some fixed final conversion in a recycle reactor, there must be a particular recycle ratio ‘R’ that minimizes the reactor volume or space time.

Question 40

ratio of moles of desired product formed at any instant to moles of reactant (A) reacted at any instant; it is a function of Ca

Answer 40

instantaneous fractional yield

Question 41

is the mean of the instantaneous fractional yields at all points within the reactor

Answer 41

overall fractional yield

Question 42

both instantaneous and overall fractional yield depend on the ______ within the reactor

Answer 42

type of flow

Question 43

is the ratio of moles of desired product to moles of undesired product

Answer 43

selectivity

Question 44

ratio of moles of product formed to moles of reactant either fed or consumed

Answer 44

yield

Question 45

how does the concentration level of reactants affect the product distribution in parallel reactions?

Answer 45

High reactant concentration favors the reaction of higher order. Low reactant concentration favors the reaction of lower order. The concentration level has no effect on the product distribution for reactions of the same order