Multiple Choice Questions on Catalyst and Catalysis

MCQ on Catalyst and Catalysis with Answers Pdf

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Important Points to Remember about Catalyst and Catalysis  : 

  1. Substances which accelerate the rate of a chemical reaction and themselves remain chemically and quantitatively unchanged after the reaction are known as catalyst and the phenomenon is known as catalysis.
  2. Catalysis can be broadly divided into two groups (A) Homogeneous catalysis : When the reactants and the catalyst are in the same phase (i.e. liquid or gas), the process is said to be homogeneous catalysis.
  3. Surface catalysis or heterogeneous catalysis :  The catalytic process in which the reactants and the catalyst are in different phases is known as heterogeneous catalysis
  4. Promoters : Those substances which do not themselves act as catalysts but their presence increases the activity of catalyst are called catalytic promoters. Example : In Haber process for the synthesis of ammonia, Fe is catalyst while molybdenum (Mo) acts as a promoter.
  5. Inhibitors : The substance which decreases the rate of chemical reaction is called inhibitor. It increases the activation energy for the reaction
  6. Catalytic poison : The substance whose presence decreases or destroys the activity of a catalyst is called catalytic poison.


General characteristics of catalysts :

  1. A catalyst remains unchanged in mass and chemical composition but can change their physical state.
  2. Only a very small amount of catalyst is sufficient to catalyse a reaction.
  3. A catalyst does not initiate a reaction.
  4. When a catalyst is a solid, it is usually more efficient when used in finely divided form.
  5. Generally catalyst does not change the nature of products.
  6. A catalyst does not change the equilibrium state of a reversible reaction but helps to decrease time to achive the equilibrium state or position of equilibrium.
  7. Catalysts are generally specific in nature.
  8. Catalyst can change rate constant of the reaction.
  9. Catalysts participate in mechanism of reaction.
  10. Catalyst does not change enthalpy of reaction, free energy and entropy because they are state function.


Catalyst MCQ Questions and Answers

1. A catalyst is more effective in_________

(1) Finely powdered state

(2) Colloidal state

(3) Rough surface

(4) All of these

Answer: 4


2. Which of the following is affected by catalyst? 

(1) ∆H 

(2) ∆S 

(3) ∆G 

(4) Ea

Answer: 4


3. Which of the following statement is incorrect_________

(1) Enzymes exist in colloidal state

(2) Enzymes are catalysts

(3) Enzymes can catalyse any reaction

(4) Urease is an enzyme

Answer: 3


4. Which of the following is a catalytic poison?

(1) Potassium nitrate

(2) Aluminium nitrate

(3) Aluminium oxide

(4) Chlorine

Answer: 3


5. Which of the following is used as a catalytic promoter?

(1) chlorine

(2) nitrate

(3) bromine

(4) helium

Answer: 2


6. Which of the following is known as Lindlar’s catalyst?

(1) Na in liquid NH3

(2) Pt in ethanol

(3) Pd with BaSO4

(4) Ni in ethanol

Answer: 3


7. Efficiency of the catalyst depends on its_________

(1) Molecular weight

(2) Number of free valencies

(3) Physical state

(4) Amount of reactant used

Answer: 2


8. How does a catalyst increase the rate of a reaction?

(1) By forming an intermediate complex

(2) By increasing activation energy

(3) By lowering the activation energy

(4) By changing equilibrium constant

Answer: 3


9. Which of the following types of metals make the most efficient catalysts_________

(1) Transition metals 

(2) Alkali metals

(3) Alkaline earth metals 

(4) Radioactive metals

Answer: 1


10. Which one of the following statements is  incorrect about enzyme catalysis?

(1) Enzymes are denaturated by ultraviolet rays and

at high temperature

(2) Enzymes are least reactive at optimum

temperature

(3) Enzymes are mostly proteinous in nature

(4) Enzyme action is specific

Answer: 2


11. Which of the following statements about the catalyst is true?

(1) A catalyst makes the reaction feasible by making ΔG more negative.

(2) A catalyst makes equilibrium constant more favourable for forward reaction.

(3) A catalyst accelerate rate of reaction by bringing down the activation energy.

(4) A catalyst always increases the rate of reaction

Answer: 3


12. Which is not the correct statement for a catalyst__________

(1) It does not alter activation energy.

(2) It provides an alternate mechanism with a lower energy of activation

(3) Catalyst may form intermediates with the reactants

(4) Action of enzyme catalyst is always specific

Answer: 1


13. Shape selective catalysts are so called because of___________

(1) The shape of the catalysts

(2) The specificity of the catalysts

(3) The size of the pores of the catalysts which can trap only selective molecules

(4) Their use for only some selected reactions

Answer: 3


14. In a reversible reaction a catalyst_________

(1) Increases the rate of forward reaction only

(2) Increases the rate of forward reaction to a greater extent than that of the backward reaction

(3) Increases the rate of forward reaction and decreases that of the backward reaction

(4) Increases the rate of forward and backward reaction equally

Answer: 4


15. Which of the following will decrease the rate of reaction?

(1) Catalytic poison

(2) Positive catalyst

(3) Negative catalyst

(4) Catalytic promoters

Answer: 1


16. Which is false for catalyst__________

(1) A catalyst can initiate a reaction

(2) It does not alter the position of equilibrium in a reversible reaction

(3) A catalyst remains unchanged in quantity and composition at the end of reaction

(4) Catalysts are sometimes very specific in respect of a reaction

Answer: 1


17. The catalytic efficiency of two distinct enzymes can be compared based on which of the following factor?

(1) km

(2) product formation

(3) size of the enzymes

(4) ph of optimum value

Answer: 1