Chemical Reaction Quiz 6

1 / 50

Pick out the wrong statement?

Catalytic activity of enzyme catalysed reactions which is affected by temperature, pH value & chemical agents, is maximum at a temperature of about 45?C

Equilibrium concentrations in enzyme catalysed reactions can be calculated by using the thermodynamic properties of substrates & products

Most of the enzyme catalysed reactions involve at least two substrates

Enzymes help in increasing the activation energy of the reaction

2 / 50

Sum of the powers of the concentration terms in the rate equation is called the ______ of the reaction?

Order

Overall order

None of these

Molecularity

3 / 50

Second order consecutive irreversible reaction as shown in the bellow figure, were carried out in a constant volume isothermal batch reactor with different initial feed compositions. Reactor temperature was same in all the cases. In experiments where the ratio of 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, concentration of B decreased monotonically with time right from the beginning. What is the ratio of the two rate constants (k1/k2) ?

2-Jan

4-Jan

4 / 50

Rate of a chemical reaction is independent of the concentration of the reactants for a __________ reaction?

Third order

Zero order

Consecutive

None of these

5 / 50

The conversion for a first order liquid phase reaction. A ? B in a CSTR is 50%. If another CSTR of the same volume is connected in series, then the % conversion at the exit of the second reactor will be_______?

100

6 / 50

The catalyst in a second order reversible reaction increases the rate of the forward reaction_____?

And backward reaction equally

Only

And decreases that of backward reaction

To a greater extent than that of the backward reaction

7 / 50

Pick out the wrong statement?

When the reaction rate is independent of temperature, the reaction is said to be of zero order

The ratio of volumes of plug flow reactor to that of mixed reactor is always less than one for identical feed composition, flow rate, conversion and for all positive reaction orders

The integral method of analysing kinetic data is used when the data is scattered

The differential method of analysing kinetic data requires more accurate or larger amounts of data

8 / 50

Semibatch reactor is preferred, when a/an___________?

A highly exothermic reaction is to be controlled

A gas is to be reacted with liquid (e.g. hydrogenation of fat)

Undesirable side reaction (at high concentration of one of the reactants) is to be avoided

All A., B., and C.

9 / 50

Signal normally used to study non-ideal flow by stimulus response technique is ________ input?

Both A. & B.

Neither A. nor B.

Pulse

Step

10 / 50

Pick out the wrong statement?

A higher temperature favours the reaction of higher activation energy

A catalyst increases the potential energy barrier over which the reactants must pass to form products

Exit age description function E. and internal age distribution function (I) are related as, E = -(dI/d?)

Chemisorption studies are useful in the determination of catalyst surface area and pore size distribution

11 / 50

The eddy diffusivity for a liquid in plug flow must be__________?

Between 0 and 1

12 / 50

Reactions with high activation energy are_______?

Very temperature sensitive

Always irreversible

Temperature insensitive

Always reversible

13 / 50

The dispersion number of perfect mixed flow is___________?

< 2100

> 150

14 / 50

Pick out the wrong statement?

The intercept of the Arrhenius plot is called the ?activation energy?

A particular chemical reaction is more temperature sensitive at low temperatures

Non-ideal flow takes place in reactors due to recycling, channeling or by creation of stagnant regions

A very high value of equilibrium constant, K (K >> 1) indicates that the reaction is practically irreversible in nature

15 / 50

The conversion in a mixed reactor/accomplishing a reaction A ? 3R is 50% when gaseous reactant ?A? is introduced at the rate of 1 litre/second and the leaving flow rate is 2 litres/second. The holding time for this operation is ________ second?

0.5

16 / 50

The concentration of A in a first order reaction, A ? B, decreases_______?

Logarithmically with time

Exponentially with time

Linearly with time

Very abruptly towards the end of the reaction

17 / 50

Rate of a chemical reaction is not affected by the______?

Reactant?s concentration

Number of molecules of reactants taking part in the reaction

Temperature

Catalyst

18 / 50

Slurry reactors are characterised by the__________?

Lack of intraparticle diffusion resistance

Presence of two mobile phases

Both A. and B.

Neither A. nor B.

19 / 50

Rate determining step in a reaction consisting of a number of steps in series is the _______ step?

Slowest

Data insufficient; can?t be predicted

Intermediate

Fastest

20 / 50

Recycling back of outlet stream to the reactor from an ideal CSTR carrying out a first order liquid phase reaction will result in _______ in conversion?

Either A. or B., depends on the type of reaction

Decrease

Increase

No change

21 / 50

Reaction of benzene with chlorine gas to produce tri-chlorobenzene exemplifies a/an _______ reaction?

Consecutive

None of these

Parallel

Elementary

22 / 50

Sometimes, batch process is preferred over continuous process, when the product_____?

Neither A. nor B.

Both A. & B.

Quality & yield cannot be achieved in continuous processes, because of long residence time

Sales demand is fluctuating

23 / 50

Rate of a chemical reaction is not influenced by the___________?

Catalyst

Temperature

Reactants concentration

Number of molecules of reactants taking part in a reaction

24 / 50

The ?E? curve for a non-ideal reactor defines the fraction of fluid having age between t and t + dt _______?

Averaged over the inlet and outlet

In the reactor

At the outlet

At the inlet

25 / 50

Pick out the wrong statement?

If the rate of an irreversible reaction, A + B ? 2C is k.CA.CB, then the reaction is always elementary

In a first order reaction, A ? products; the reaction becomes slower as it proceeds, because the concentration of A decreases and the rate is proportional to the concentration of A

According to the penetration theory, the mass transfer co-efficient decreases, if the exposure time of an eddy to the solute decreases

Transition state theory approaches the problem of calculating reaction rates by concentrating on the idea of activated complexes

26 / 50

Pick the WRONG design guideline for a reactor in which the reactions, A ? R (desired) and A ? S (undesired) are to take place. The ratio of the reaction rates is rR/rS = (k1/k2). CA a-b ?

Avoid recycle, when a > b

Use high pressure and eliminate inerts, when a > b

Use batch reactor or plug flow reactor, when a > b

Use CSTR with a high conversion, when a > b

27 / 50

Rate constant ?k? and absolute temperature ?T? are related by collision theory (for bimolecular) as________?

k ? T1.5

k ? ?T

k ? exp(-E/RT)

k ? T

28 / 50

Shift conversion reaction__________?

Is non-catalytic

Converts CO to CO2 with steam

Converts N2 and H2 into NH3

Is highly exothermic

29 / 50

Space time in flow reactor is______?

The reciprocal of the space velocity

Usually equal to the residence time

Both A. and B.

A measure of its capacity

30 / 50

Rate constant for a first order reaction does not depend upon reaction time, extent of reaction and the initial concentration of reactants; but it is a function of reaction temperature. In a chemical reaction, the time required to reduce the concentration of reactant from 100 gm moles/litre to 50 gm moles/litre is same as that required to reduce it from 2 gm moles/litre to 1 gm mole/litre in the same volume. Then the order of this reaction is ?

31 / 50

The catalyst in a first order chemical reaction changes the__________?

Equilibrium constant

Heat of reaction

Heat of formation of the product

Activation energy

32 / 50

Reverse reaction in a chemical equilibrium is favoured by the_________?

Removal of one of the products regularly

Increase in the concentration of one of the products

None of these

Increase in the concentration of one of the reactants

33 / 50

The effectiveness factor for large value of Thiele modulus [L?(K/D1)] of a solid catalysed first order reaction is equal to (where, L = length of the reactor, cm, D1 = diffusion co-efficient, cm2/second) ?

1/[L?(K/D1)]

L ?(K/D1)

34 / 50

Space velocity______?

Is the maximum feed rate per unit volume of reactor for a given conversion

All A., B. and C.

Is a measure of the ease of the reaction

Describes the extensive operating characteristics of a tubular flow reactor

35 / 50

Rate of an autocatalytic chemical reaction is a function of _____?

All A., B. and C.

Pressure only

Composition only

Temperature only

36 / 50

Promoter is added to the catalyst to improve its______?

Porosity

None of these

Surface area

Sensitivity

37 / 50

Pick out the wrong statement?

Use of different catalysts in a reversible catalytic chemical reaction does not change the equilibrium composition

Alumina is added as a promoter to iron catalyst in ammonia synthesis reaction

Activation energy for a reaction is obtained from the intercept of the Arrhenius plot

Presence of inerts affects the equilibrium conversion of

38 / 50

Reaction rate of a first order reaction, which is half completed in 23 minutes will be __________?

0.03 sec-1

0.03 min-1

0.03 hr-1

0.05 min-1

39 / 50

The catalytic converter for conversion of SO2 to SO3 by contact process should have a feed with SO2 content between_____?

12-15 %

7-10 %

2-5 %

20-25 %

40 / 50

The conversion of a reactant, undergoing a first order reaction, at a time equal to three times the half life of the reaction is ?

0.875

0.5

0.425

Data insufficient to calculate

41 / 50

Specific rate constant for a second order reaction___________?

Depends on the nature of the reactants

Varies with temperature

Both B. and C.

Is independent of temperature

42 / 50

Promoter_______?

Alters the position of equilibrium in a reversible reaction

All A., B. and C.

Increases the number of active centres by increasing the unevenness of catalyst surface and by creating discontinuities in the crystals

Initiates a chemical reaction and is a catalyst by itself

43 / 50

The catalytic activity of enzymes is due to their capacity to lower the _______ energy?

Potential

Kinetic

None of these

Activation

44 / 50

The dimensions of rate constant for reaction 3A ? B are (l/gm mole)/min. Therefore the reaction order is________?

45 / 50

Pure ethanol vapor is fed to a reactor packed with alumina catalyst, at the rate of 100 kmole / hr. The reactor products comprise: ethylene: 95 kmole / hr, water vapour: 97.5 k mole / hr and diethyl ether: 2.5 kmole/hr. The reactions occuring can be represented by: C2H5OH ? C2H4 + H2O 2C2H5OH ? C2H5 ? O ? C2H5 + H2O The percent conversion of ethanol in the reactor is_________?

100

2.5

97.5

46 / 50

Sulphuric acid is used as a catalyst in the________?

Gas phase oxidation of SO2 in chamber process

Hydrogenation of oils

None of these

Alkylation of hydrocarbons

47 / 50

Rate of a gaseous phase reaction is given by the reaction shown in the bellow figure. The unit of rate constant is___________?

atm.(hr)-1

(atm)-1.(hr)-1

(hr)-1

(atm)-1

48 / 50

The conversion for a second order, irreversible reaction (constant volume) as shown in the bellow figure, in batch mode is given by_______?

(k2 . CA0 . t)/ (1 + k2 . CA0 . t)2

(k2 . CA0 . t)/ (1 + k2 . CA0 . t)

(k2 . CA0 . t)2/ (1 + k2 . CA0 . t)

1/(1 + k2 . CA0 . t)

49 / 50

Space time equals the mean residence time___________?

For narrow diameter tubular reactor

When the density of the reaction mixture is constant

For large diameter tubular reactor

For CSTR

50 / 50

Radioactive decay follows _______ order kinetics?

First

Zero

Second

Third

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