Catalysis engineering course multiple choice question

increases the free energy change in the reaction.. does not increases and decreases the free energy change in the reaction.. can either decreases or increases the free energy change depe

HO CHI MINH CITY UNIVERSITY OF FOOD INDUSTRY

Falculty of Chemical Engineering

CATALYSIS ENGINEERING COURSE

Multiple Choice Question

January - 2024

Contents

Chapter 1- 2 1 Chapter 3 - 4 8

Chapter 1- 2

1 The addition of catalyst during a chemical reaction alters which of the following quantities? A Entropy B Internal energy

C Enthalpy D Activation energy

2 A catalyst is a substance which ………

A increases the equilibrium concentration of the product

B changes the equilibrium constant of the reaction

C shortens the time to reach equilibrium

D supplies energy to the reaction

3 A catalyst … ………

A increases the free energy change in the reaction

B decreases the free energy change in the reaction

C does not increases and decreases the free energy change in the reaction

D can either decreases or increases the free energy change depending on what catalyst we use

4 Regarding criteria of catalysis which one of the following statements is not true? A The catalyst is unchanged chemically during the reaction

B A small quantity of catalyst is often sufficient to bring about a considerable amount of the reaction

C In reversible reaction, the catalyst alters the equilibrium position

D The catalyst accelerates the rate of reaction

5 The work of enzymes in living system is ………

A oxygen transfer B to provide immunity

C to catalyze biochemical reactions D to provide energy

6 A chemical reaction is catalyzed by catalyst X So X ………

A increases the activation energy of reaction

B does not affect equilibrium constant of reaction

C decreases the rate constant of reaction

D decreases enthalpy of reaction

7 How enzymes increase the rate of reactions?

A By lowering activation energy B By increasing activation energy

C By changing equilibrium constant D By forming enzyme substrate complex

8 The process which is catalyzed by one of the products is called ……… A acid-base catalysis B autocatalysis

C negative catalysis D None of these

9 Which of the following statements about a catalyst is not true? A It lowers the energy of activation

B The catalyst altered during the reaction is regenerated

C It does not alter the equilibrium

D It does not alter the rate constant of reaction

10 A catalyst can effect reversible reaction by ………

A changing equilibrium B slowing forward reaction

C attaining equilibrium in both direction D None of these

11 Which one of the following is an example for homogeneous catalysis? A Manufacture of sulfuric acid by contact process

B Manufacture of ammonia by Haber’s process

C Hydrolysis of sucrose in presence of dilute hydrochloric acid

D Hydrogenation of oil

12 The efficiency of enzyme catalysis is due to its capacity to ………

A form a strong enzyme-substrate complex B change the shape of the substrate

C lower the activation energy of the reaction D form a colloidal solution in water

13 Which of the following reaction is an example for homogeneous catalysis?

B lowers the activation energy of reacting molecules

C is capable of reacting with any one of the reactants

D can not be recovered chemically unchanged at the end of a chemical reaction

15 The equilibrium constant of a catalytic chemical reaction due to the presence of a catalyst

A increases B decreases

C remains unaffected D unpredictable from the data

16. When a catalyst increases the rate of forward reaction, the value of rate constant ……… …

A increases B decreases C does not change D becomes infinite

17. In autocatalytic reactions, ………

A one of the reactants acts as a catalyst B one of the products acts as a catalyst

C catalysts have very high selectivity D no catalyst is used

18 The reason why a catalyst increases the rate of reaction is that, it ………

A decreases the energy barrier for reaction B increases the activation energy

C decreases the molecular collision diameter D None of these

19 A reaction which is catalyzed by a base is catalyzed by all substances which have a tendency to

A lose a proton B gain a proton C gain an electron D None of these

20 A reaction which is catalyzed by an acid is also catalyzed by any substance, which has a tendency to …………

A lose a proton B gain a proton C lose an electron D None of these

21 A catalyst ………

A increases the equilibrium concentration of the product

B changes the equilibrium constant of the reaction

C shortens the time to reach the equilibrium

D can either increase or decrease (depends on the type of catalyst)

23. Catalyst is a substance, which chemical reaction.

A increases the speed of a

B decreases the speed of a

C can either increase or decrease the speed of a

D alters the value of equilibrium constant in a reversible

24. Pick out the correct statement

A A catalyst speeds up the forward reaction but slows shown the reverse reaction

B Addition of catalyst changes the equilibrium constant

C Pressure changes do not change the equilibrium concentrations

D The composition of equilibrium is changed by catalyst.

25. Oxidation of SO2 to SO3 in the presence of nitric oxide (NO) as catalyst

What's kind of the catalyst for the above reaction?

A Homogenous catalyst

B Heterogeneous catalyst

C Heterogeneous catalysts and homogenous catalysts

D Undefined

26. Manufacture of ammonia by Haber’s process using finely divided iron as catalyst

What's kind of the catalyst for the above reaction?

A Homogenous catalyst

B Heterogeneous catalyst

C Heterogeneous catalysts and homogenous catalysts

D Undefined

27 In acid catalysis, the H+ (or a proton donated by Bronsted acid) forms an intermediate with the reactant, which then reacts to give back the proton For example, the mechanism of ketoenol tautomerism of acetone is:

Substance X is a/an ……

A reactant B catalysts C product D intermediate

28. For example of Homogeneous Catalytic Mechanism, the reaction takes place by a two-step mechanism as shown below:

Reaction intermediate is ………

29. Which statement about catalyst is universally correct?

A A catalyst does not take part in reaction

B A catalyst remains unchanged physically and chemically

C A catalyst lowers the energy of activation

D A catalyst is highly specific in action

30. In a reversible reaction, a catalyst ………

A increases the rate of forward reaction only

B increases the rate of forward reaction to a greater extent than of the backward reaction

C increases the rate of forward reaction to and decreases that of the backward reaction

D increases the rate of forward and backward reaction equally

31. The decomposition of CH3CHO in presence of I2 involves: CH3CHO + I2 → CH3I + HI + CO CH3I + HI → CH4 + I2

and rate = k[CH3CHO][I2] Is I2 catalyst for the reaction?

A No; I2 is intermediate

B Yes; the first step being slow and thus rate is given = k[CH3CHO][I2]

C No; HI is catalyst for the reaction

D No; I2 is reactant for the reaction

32. Mark the incorrect statement: A catalyst …………

A alters the velocity of reaction

B changes the energy of activation of given process

C does not alter the state of equilibrium

D is a reactant required in small quantity

33 The exothermic reaction between substances A and B is presented in the plot below

Catalyst-induced preparation of the substance AB follows the pathway …

A (1) B (2) C (3) D None is correct

34 The catalyzed decomposition of hydrogen peroxide is believed to take place by a two-step path:

Step 1: H2O2 (aq) + I– (aq) → H2O + IO– (aq)

Step 2: H2O2 (aq) + IO– (aq) → H2O + O2 (g) + I– (aq)

2H2O2 (aq) → 2H2O + O2 (g)

Choose the correct statement about this reaction

A I– is a catalyst B H2O is a reactant

C IO– is a product D O2 is an intermediate

takes place by mechanism as follow:

(X)

Substance X takes part in this reaction as a/an ………….…

A catalyst B activated complex C intermediate D inhibitor

takes place by mechanism as follow:

The energy profile of the reaction should be:

37 The mechanism of the reaction: A + 2B → D + E; H = –ve is

Step I: A + 2B → C (slow) Step II: C → D + E (fast)

The energy profile of the reaction should be:

38 Based on the following reaction profile, how is the enthalpy change of the reaction?

A Negative B Positive C Zero D Infinitive

39 Based on the following reaction profile, how many transition states are there in the reaction:

41 The following graph shows two different reaction pathways for the same overall reaction at the

same temperature Choose the correct statement

A The reaction rate is faster for the red path than for the blue path

B The equilibrium constants are different in two paths

C For both paths, the rate of the reverse reaction is faster than the rate of the forward reaction

D The energy change ∆E is the same for both paths

Chapter 3 - 4

1 The phenomenon of concentrations of molecules of a gas or liquid at a solid surface is called

A. absorption B. adsorption C. catalysis D. None of these

2 In gas masks, the poisonous gases are removed by the adsorbent by the process of _

A. absorption B. adsorption C. catalysis D. none of these

3 The adsorption of hydrogen on charcoal is

A. physical adsorption B. chemical adsorption C. sorption D. none of these

4 Heat of adsorption is defined as the energy liberated when of a gas is adsorbed on the

solid surface

A. 1 molecule B. 1 g C. 1 mole D. 1 kg

5 Which one of the following characteristics is associated with adsorption?

A. G is negative but H and S are positive

B. G, H and S all are negative

C. G and H are negative but S is positive

D. G and S are negative but H is positive

6 For physical adsorption of a gas on solid adsorbent

A. H is positive B. S is negative C. G is negative D. F is positive

7 Adsorption of gases on solid surface is generally exothermic because

A. chemical bonds are always formed

B. adsorbate decreases the surface energy of adsorbent

C. entropy increases

D. free energy increase

8 Which of the following is correct?

A. Adsorption is always exothermic

B. Adsorption is always endothermic

C. Physical adsorption is endothermic whereas chemical adsorption is exothermic

D. Chemical adsorption is endothermic whereas physical adsorption is exothermic

9. The heat of adsorption in physical adsorption lies in the range _ kJ/mole

A. – (1–10) B. – (10–400) C. – (4–100) D. – (100–400)

10 The enthalpy of adsorption in chemisorption lies in the range _ kJ/mole

A. – (40 – 400) B. – (100 – 400) C. – (4 – 100) D. – (1 – 10)

11 Physical adsorption is appreciable at

A. higher temperature B. lower temperature C. room temperature D. 100°C

12 Rate of physical sorption increases with _

A. decrease in temperature B. increase in temperature

C. decrease in pressure D. decrease in surface area

13 Which characteristic of adsorption is wrong?

A. Physical adsorption decreases with increase in temperature

B. Physical adsorption increases with increase in temperature

C. Physical adsorption is a reversible process

D. Adsorption is limited only to the surface

14 Which one of the following characteristics is not correct for physical adsorption of a gas on

solid?

A. Adsorption is reversible

B. Adsorption increase with increase in temperature

C. Absorption is spontaneous

D. Both enthalpy and entropy of adsorption are negative

15 Which one of the following is an incorrect statement for physical sorption?

A. It is a reversible process B. It requires less heat of adsorption

C. It requires activation energy D. It takes place at low temperature

16 Which one of the following is not a correct statement?

A. Physical adsorption is reversible in nature

B. Physical adsorption involves Vander Waal’s forces

C. Rate of physical adsorption increases with increase of pressure on the adsorbate

D. High activation energy is involved in physical adsorption

17 Which one of the following is not applicable to chemisorption?

A. Its heat of adsorption is high B. It takes place at high temperature

C. It is reversible D. It forms mono-molecular layers

18 Which of the following is not a characteristic of chemisorption?

A. Adsorption is irreversible

B. Adsorption decreases with increase in temperature

C. Adsorption is specific

D. Adsorption increases with increase of surface area

19 Which one of the following is not applicable to chemisorption?

A. High magnitude of ΔH B. Occurs at higher temperature

C. It is reversible D. It forms mono layer

20 The nature of bonding forces in adsorption is _

A. purely physical like Vander Waal’s force B. purely chemical

C. both, physical and chemical, always D. None of these

21 In physical adsorption, the forces associated are _

A. ionic bond B. covalent bond

C. vander Waal’s forces D. All of these

22 The nature of bonding forces in adsorption is _

A. purely physical such as Van der Waal’s forces

B. purely chemical

C. both chemical and physical always

D. None of these

23 In physical adsorption, the gas molecules are held to the solid surface by _

A. hydrogen bond B. sigma bond

C. pi bond D. van der Waals’ forces

24 The relationship between equilibrium pressure of gas and its amount adsorbed on the solid

adsorbent at constant temperature is called _

A. chemisorption B. adsorption isobars

C. adsorption isotherms D. None of these

25 The adsorption of a gas on a solid surface varies with pressure of the gas in which of the

following manner?

A. Fast → slow → independent of the pressure

B. Slow → fast → independent of the pressure

C. Independent of the pressure → fast → slow

D. Independent of the pressure → slow → fast

26 Langmuir isotherms hold at low pressure but fail at _

A. low temperature B. high pressure C. intermediate pressure D. None of these

27 Freundlich isotherms is not applicable at _

A. high pressure B. low pressure C. 273 K D. room temperature

28 How many layers are adsorbed in chemical adsorption?

A. 1 B. 2 C. 3 D. 1 or more

29 Multi-molecular layers are formed in _

A. absorption B. physical adsorption

C. chemisorption D. reversible adsorption

30 Which among the following statements is false?

A. Increase of pressure increases the amount of adsorption

B. Increase of temperature may decrease the amount of adsorption

C. The adsorption may be monolayered or multilayered

D. Particle size of the adsorbent will not affect the amount of adsorption

31 A finely divided state of catalyst is more efficient because in this state:

A less active centers are formed B. more surface area is available

C more energy is stored in the catalyst D. more molecules are formed