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ChELE > CRE > Flashcards

CRE Flashcards

1
Q

Type of reactor with uniform composition everywhere in the reactor but changes with time

a. Batch
b. PFR
c. CSTR

A

Batch

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2
Q

Type of reactor where there is no mixing of earlier and latter fluids and no overtaking

a. Batch
b. PFR
c. CSTR

A

PFR

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3
Q

“molecules must collide to react. the greater the number of collisions occuring per second, the greater is the reaction rate”

A

collision model

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4
Q

For example, in a mixture H2 and I2 at ordinary temperatures and pressures, each molecule undergoes about ________ collisions per second however only 1 in every ________ collisions produces a reaction, in production of HI from H2 and 12.

A

1010, 1013

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5
Q

Minimum value required to initiate chemical reaction

A

Activation Energy,E

accdg to Svante Arrhenius

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6
Q

The unit of k for a first order elementary reaction is

a. 1/time
b. concentration/time
c. 1/ concentration
d. 1/concentration•time

A

a

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7
Q

In which of the following cases does the reaction go farthest to completion?

a. k = 10^2
b. k = 10^-2
c. k = 10
d. k=1

A

a.
higher k = further into completion

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8
Q

The activation energy, E of a reaction may be lowered by

a. increasing the temperature
c. adding a catalyst
b. decreasing the temperature
d. removing the products of the reaction

A

c

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9
Q

The mechanism of a reaction can sometimes be deduced from

a. the temperature dependency of the rate
b. the net reaction
c. the rate equation
d. the activation energy

A

c

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10
Q

The law governing the kinetics of a reaction is the law of

a. constant composition
c. constant temperature
b. chemical equilibrium
d. mass action

A

d

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11
Q

The equilibrium constant in a reversible chemical reaction at a given temperature

a. depends on the initial concentration of the reactants
b. depends on the concentration of one of the products at equilibrium
c. does not depend on the initial concentrations
d. is not a characteristic of the reaction

A

c

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12
Q

Which of the following statements is the best explanation for the effect of increase in temperature on the rate of reaction?

a. It increases the number of particles with the necessary activation energy
b. It enables the reacting particles with the necessary activation energy
c. It lowers the activation energy for the reaction
d. It enables the activated complex to be more easily converted to the products

A

a

Activation energy is inversely proportional to the rate of reaction. As the activation energy increases, the rate of reaction decreases.

As the temperature increases, the activation energy decreases. because higher temp = MOLECULES ALSO CARRY MORE KINETIC ENERGY. (number of particles with the necessary activation energy)

Thus, less activation energy is needed.

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13
Q

If the rate of reaction is independent of the concentration of the reactants, the reaction is said to be

a. first order
c. second order
b. third order
d. zero order

A

d

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14
Q

The specific rate of reaction is primarily dependent on

a. time of reaction
b. heat of reaction
c. temperature
d. concentration of the reactant

A

c.
specific rate of reaction or rate constant (k)

Rate constant of a reaction depends on its TEMPERATURE only and not affected by concentration.

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15
Q

The rate of reaction is not influenced by

a. concentration of the reactants
b. molecularity of the reaction
c. nature of reactants
d. temperature

A

b

Molecularity is the number of reacting species involved in simultaneous collisions in an elementary or simplest reaction.

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16
Q

Chemical reaction rates in solution do not depend to any extent upon

a. pressure
b. temperature
c. concentration
d. catalyst

A

d

17
Q

The overall order of reaction for the elementary reaction A + 2B —> C is

a. 0
b. 1
C. 2
d. 3

A

d

18
Q

The net rate of reaction of an intermediate is

a. Zero
b. infinity
c. greater than zero
d. less than zero

A

a

19
Q

The collision theory of chemical reactions maintains that

a. A chemical reaction occurs with every molecular collision.
b. Reactions in the gas phase are always first order.
c. Reaction rates are of the order of molecular speeds.
d. Rate is directly proportional to the number of collisions per second

A

d

20
Q

A reaction is known to be first order in A. A straight line will be obtained by plotting

a. log Ca versus time
b. Ca versus time
c. log Ca versus reciprocal time
d. 1/Ca versus time

A

a

21
Q

If the reaction, 2A —> B + C is second order, which of the following plots will give a straight line?

a. Ca^2 vs. time
b. 1/Ca vs. time
c. log Ca vs. time
d. Ca vs. time

A

b

22
Q

The activation energy of a reaction can be obtained from the slope of a plot of

a. log k vs 1/T
b. k vs log T
c. log k vs T
d. k vs log 1/T

A

a

23
Q

A pressure cooker reduces cooking time because

a. The heat is more evenly distributed.
b. The higher pressure tenderizes the food.
c. The boiling point is elevated.
d. A large flame must be used.

A

c

24
Q

A catalyst can

a. shift the equilibrium of reaction
b. diminish the activation energy
c. increase the rate constant of forward reaction
d. decrease the pressure

A

c.

A catalyst is something that lowers the activation energy; in biology it is an enzyme. The catalyst speeds up the rate of reaction without being consumed.

Activation energy is defined as the minimum amount of extra energy required by a reacting molecule to get converted into product. It can also be described as the minimum amount of energy needed to activate or energize molecules or atoms so that they can undergo a chemical reaction or transformation.

25
Q

It states that the rate of a chemical reaction is proportional to the activity of the reactants.

a. Law of Mass Action
c. Le Chatelier’s Principle
b. Hess’ Law
d. Second Law of Thermodynamics

A

a

26
Q

Rapid increase in the rate of a chemical reaction even for small temperature increase is due to

a. rapid increase in kinetic energy of molecules
b. rapid increase with temperature of the fraction of molecules with energies in excess of activation energy
c. rapid increase in collision frequency
d. increase in activation energy

A

d

27
Q

The half-life of a material undergoing second order decay is

a. proportional to the square of initial concentration
b. independent of initial concentration
c. proportional to initial concentration
d. inversely proportional to initial concentration

A

d

28
Q

The composition of the reaction component varies from position to position alor flow path in a/an

a. CSTR
b. adiabatic reactor
c. batch reactor
d. plug-flow reactor

A

d

29
Q

_________ reactions do not have direct correspondence between stoichiometry and the rate equation

A

Non elementary

30
Q

T or F

The faster chemical reaction rate at higher temperature is due to an increase in rate constant with increasing temperature

A

true

ChELE (21 decks)

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