Chemistry by Inam Jazbi: X Chemistry Multiple Choice Questions (MCQs) on Chemical Equilibrium

X Chemistry Multiple Choice Questions (MCQs) on Chemical Equilibrium

Multiple Choice Questions (MCQs) on Chemical Equilibrium from Textbook

1. Which one of the following statements is FALSE about dynamic equilibrium?

(a) Concentration of reactant and products are not changed

(b) It takes place in a close container

(d) Equilibrium cannot be disturbed by any external stress.

2. When the magnitude of K_c is small, indicates

(a) Reaction mixture contains most of the reactant

(b) Reaction mixture contains most of the product

(d) Reaction goes to completion

3. Q_c can be defined as

(a) ratio of product and reactant

(b) ratio of molar concentration of product and reactant at specific time

(d) ratio of molar concentration of product and reactant raised to the power of coefficient

4.Consider the following reaction and indicates which of the following best describe equilibrium constant expression K_c

4NH₃_(g) + 5O₂_(g) ⇌ 4NO_(g) + 6H₂O_(g)

5. For which system does the equilibrium constant, K_c has units of concertation?

(a) N₂_(g) + 3H₂_(g) ⇌ 2NH₃_(g)

(b) N₂_(g) + O₂_(g) ⇌ 2NO_(g)

(d) CO₂_(g) + H₂_(g) ⇌ CO_(g) + H₂O_(g)

6. A reaction which is never goes to completion is known as reversible reaction. Reversible reaction is represented by

(a) Double straight line

(b) Single arrow

(d) Doted lines

7. The unit of K_c for reaction; N₂_(g) + O₂_(g) ⇌ 2NO_(g)

(a) mol dm⁻³

(b) mol⁻² dm⁶

(d) no unit

8. The system is stable in equilibrium when:

(a) Q_c = K_c

(b) Q_c > K_c

(d) None of these

9. The value of K_c increases when

(a) [Reactant] = [product]

(b) [Product] is more

(d) [Product] is less

10.Which of the following represent backward reaction?

(a) (i) and (ii)

(b) (ii) only

(d) (iii) only

Answers of MCQs on Chemical Equilibrium from Text Book

1. D

2. A

3. B

4. A

5. A

6. D

7. B

8. B

9. A

10. B

Multiple Choice Questions (MCQs) on Chemical Equilibrium from External Source

1. A chemical reaction is at equilibrium when:

(a) Rate of forward reaction > Rate of reverse reaction

(b) Rate of forward reaction < Rate of reverse reaction

(d) All of the above

2. In a chemical reaction equilibrium is said to have been established when:

(a) Concentration of reactants and products are equal

(b) Velocities of opposing reactions become equal

(d) Opposing reactions cease.

3. A chemical reaction A ⇌ B is said to be in equilibrium when:

(a) Complete conversion of A to B has taken place

(b) Complete conversion of A to B is only 50% complete

(d) The rate of transformation of A to B is just equal to the rate of transformation of B to A in the system.

4. Which of the following statement is WRONG regarding chemical equilibrium?

(a) At equilibrium two opposing chemical reactions are proceeding in opposite direction at the different rate

(b) At equilibrium there is no change in the concentration of reactant and product

(d) Chemical equilibrium can be distributed by changing conditions like concentration, pressure, temperature

5. Which one of the following is NOT a reversible reaction?

(a) Oxidation of SO₂ into SO₃

(b) Decomposition of potassium chlorate

(d) Formation of Ammonia from its constituent elements or Esterification

6. Which one is INCORRECT regarding K_c?

(a) It is a ratio b/w two rate constants and it has no unit when Δn = 0

(b) It remains constant at all temperature

(d) It is independent of the original concentration of reactants

7. The value of K_c that lies midway between 10⁻²to 10² indicates that

(a) Forward reaction goes to completion

(b) Reverse reaction goes to completion

(d) All of the above.

8. The value of K_c more than 10² indicates that

(a) Forward reaction goes to completion

(b) Reverse reaction goes to completion

(d) All of the above.

9. The value of K_c less than 10⁻² indicates that

(a) Forward reaction goes to completion

(b) Reverse reaction goes to completion

(d) All of the above.

10. Which one of the following factor will favor the reverse change?

(a) Increase in concentration of one of the reactant

(b) Removal of the products regularly

(d) None of the above.

11. When H₂ and I₂ are mixed & equilibrium is attained, then

(a) The reaction stops completely

(b) HI dissociates completely

(d) None of these

12. Which of the following is a characteristic of a reversible reaction?

(a) It never proceeds to completion

(b) It can be influenced by a catalyst

(d) Number of moles of reactants and products are equal

13. At equilibrium, __________.

(a) the rates of the forward and reverse reactions are equal

(b) the rate constants of the forward and reverse reactions are equal

(d) All of them

14. How is the reaction quotient used to determine whether a system is at equilibrium?

(a) The reaction is at equilibrium when Q < K_eq

(b) The reaction is at equilibrium when Q > K_eq

(d) The reaction is at equilibrium when Q = K_eq

15. 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

(d) Is not characteristic of the reaction

16. When a system is at equilibrium states:

(a) The concentration of reactants and products becomes equal

(b) The opposing reactions (forward and reverse) stop

(d) Active mass of all reacting species becomes constant.

17. Which one of the following statement is NOT correct about active mass?

(a) Rate of reaction is directly proportional to active mass

(b) Active mass is taken in molar concentration

(d) Active mass of all reacting species at equilibrium becomes equal.

18. The characteristics of reversible reactions are the following except;

(a) products never recombine to form reactants

(b) they never complete

(d) they have a double arrow between reactants and products

19. When the magnitude of K_c is very large it indicates;(a) reaction mixture consists of almost all products

(b) reaction mixture has almost all reactants

(d) reaction mixture has negligible products

20. When the magnitude of K_c is very small it indicates

(a) equilibrium will never establish

(b) all reactants will be converted into products

(d) the amount of products is negligible

21. At dynamic equilibrium;

(a) the reaction stops to proceed

(b) the amount of reactants and products are equal

(d) The reaction can no longer be reversed

22. In an irreversible reaction, dynamic equilibrium;

(a) never establishes

(b) establishes before the completion of reaction

(d) establishes readily

23. A reverse reaction is one that

(a) which proceeds from left to right

(b) In which the reactants react to form products

(d) which speeds up gradually

24. The reaction which never goes to completion is called:

(a) Exothermic reaction

(b) Endothermic reaction

(d) Irreversible rxn

25. The rate at which substance react is directly proportional to its active mass and the rate of chemical reaction is proportional to the product of active masses of the reacting substances. It is called

(a) Law of mass action

(b) Rate Law

(d) None of them

26. In K_c expression, the active masses of ………….. appear in numerator

(a) Products

(b) Reactants

(d) None of them

27. In K_c expression, the active masses of …….. appear in denominator

(a) Products

(b) Reactants

(d) None of them

28.In which of the following case does the reaction go farthest to completion

(a) K_c = 10²

(b) K_c = 10⁻²

(d) K_c = 1

29. In which of the following case does the reaction not go farthest to completion

(a) K_c = 10²

(b) K_c = 10⁻²

(d) K_c = 1

30. A catalyst speeds up the rate of ……….. reaction.

(a) Forward

(b) Backward

(d) None of them

31. The reaction between alcohol and acid is called

(a) Hydrolysis

(b) Neutralization

(d) Esterification

32. For a reversible reaction, if the concentration of the both the reactants are doubled, then equilibrium constant is:

(a) Also doubled

(b) halved

(d) Not changed

33. The value of K_c does not depend on _______.

(a) Temperature

(b) Initial concentration

(d) None of them

34. If K_c is very large, then reaction is considered to be _______

(a) Reversible

(b) Irreversible

(d) None of them

35. In a reversible chemical reaction having two reactants in equilibrium, if the concentration of the reactants are doubled then equilibrium constant will

(a) Also be doubled

(b) Remains the same

(d) Be halved

36. For the reaction, A + B ⇌ C, the equilibrium constant unit is

(a) dm³ mol^‒

(b) mol dm^‒3

(d) mol²dm^‒3

Reason

37. The reaction in which the products do not recombine to form reactants are called;

(a) Reversible reactions

(b) Irreversible reactions

(d) Addition

38. The reaction in which the products can recombine to form reactants are called:

(a) Reversible reactions

(b) Irreversible reactions

(d) Addition

39 The colour of iodine is:

(a) Purple

(b) Black

(d) Pink

40. The colour of hydrogen iodide is:

(a) Colourless

(b) Black

(d) Pink

41. When the rate of the forward reaction takes place at the rate of reverse action, the composition of the reaction mixture remains constant it is called:

(a) Static equilibrium

(b) Dynamic equilibrium

(d) All

42. Guldberg and Waage put forward law of mass action in

(a) 1860

(b) 1864

(d) 1879

43. The %age of nitrogen and oxygen in our atmosphere is

(a) 80

(b) 90

(d) 99

44. Which gas is used to prepare ammonia?

(a) N₂

(b) O₂

(d) S

45. Which gas is used to manufacture king of chemicals sulphuric acid?

(a) N₂

(b) O₂

(d) SO₂

46. Equilibrium constant has no unit when number of moles of reactants and products are;

(a) same

(b) different

(d) none

47. For reactions having large Kc value, the reaction proceeds to;

(a) Completion

(b) equilibrium state

(d) None

48. For the reaction, 2A_(g) + B_(g) ⇌ 3C_(g) the expression for the equilibrium constant is:

(a) [2A][B]/[3C]

(b) [A]²[B]/[C]³

(d) [C]³/[A]²[B]

49. Reactions which have comparable amounts of reactants and products at equilibrium state have;

(a) very small K_c value

(b) very large K_cvalue

(d) none of these

50. Nitrogen and hydrogen were reacted together to make ammonia

N₂ + 3H₂ ⇌ 2NH₃ K _c= 2.86 mol⁻²dm⁶

What will be present in the equilibrium mixture?

(a) NH₃ only

(b) N₂, H₂ and NH₃

(d) H₂only

51. For a reaction between PCl₃ and Cl₂ to form PCl₅, the units of Kc are;

(a) mol dm⁻³

(b) mol⁻¹ dm⁻³

(d) mol dm³

Explanation; (c)

Unit of K_c = (concentration)^∆n

Þ (mol¹ dm⁻³)^1‒2

Þ (mol¹ dm⁻³)^‒1

Þ mol⁻¹ dm³

52. The two major components of atmosphere are

(a) carbon and nitrogen

(b) Nitrogen and oxygen

(d) None of these

53. Which type of reactions do not go to completion?

(a) Irreversible reaction

(b) Reversible reactions

(d) Decomposition

54. Which type of reaction speed up gradually?

(a) Irreversible reaction

(b) Reversible reactions

(d) Decomposition

55. Which type of reactions take place in both directions?

(a) Addition reactions

(b) Reversible reactions

(d) Decomposition

56. In a chemical reaction, the substance that combine are called;

(a) reactants

(b) products

(d) material

57. Dynamic means, reaction is;

(a) in forward direction

(b) still continuing

(d) stop

58. The forward reaction takes place:

(a) right to left

(b) left to right

(d) only to left

59. The units of molar concentration:

(a) mol.dm⁻²

(b) mol.dm⁻¹

(d) mol.dm⁻³

60. Equilibrium constant value “K_c“ is equal to;

(a) K_f/K_r

(b) K_r/K_f

(d) Q_c/K_r

61. Which chemical is called king of chemicals?

(a) KNO₃

(b) H₂SO₄

(d) NHO₃

62. The rate at which substance react is directly proportional to its active mass and the rate of chemical reaction is proportional to the product of active masses of the reacting substances. It is called

(a) Law of mass action

(b) Rate Law

(d) None of them

Explanation; (a)

In 1864, two Norwegian chemists Cato Maximillian (C.M) Guldberg (1836–1902) and Peter (P) Waage (1833–1900) studied experimentally a number of equilibrium reactions and put forward their results as a generalization known as law of mass action or equilibrium law. This law gives a quantitative relationship between the rate of reaction and the active mass (molar concentration) of reacting substances.

63. For a chemical reaction aA + bB ⇌ cC + dD, K_c expression is written as:

66. Using molar concentrations, what is the unit of K_c for the following reaction?

(a) M^‒2

(b) M²

(d) M

Explanation; (b)

Unit of K_c = (concentration)^∆nÞ (M)^3‒1Þ M²

65. What is the equilibrium expression for the reaction;

P_4(s) + 5O_2(g) ⇌ P₄O_10(s)

Explanation; (d)

Concentration of pure solid or pure liquid does not appear in the equilibrium expression. Since P₄ and P₄O₁₀are solids, they are not written in the K_c formula.

K_c = 1/[O₂]⁵

66. What is the equilibrium constant (K_c) for the given reaction

2S_(s) + 3O_2(g) ⇌ 2SO_3(g)

Explanation; (d)

Concentration of pure solid or pure liquid does not appear in the equilibrium expression. Since, S is a solid reactant, so it does not include in the Kc expression.

67. Which of the following expression of K_c is correct for following reaction? N₂O₄ ⇌ 2NO₂

Explanation; (c)

[Product] = [NO₂]² = is written in numerator (coefficient becomes power of concentration)

[Reactant] = [N₂O₄] = is written in denominator

So the correct option is c.

68. Which of the following is the unit of K_c for following reaction?

N_2(g)+ 3H_2(g)⇌2NH_3(g)

Explanation; (a)

(concentration)^∆n⇒ (mole dm^–3)^2‒4⇒ (mole dm^–3)^‒2⇒ mole^–² dm⁶

69. What is the equilibrium constant, K_c, for this reaction?

CO_2(g) + 3H_2(g) ⇌ CH₃OH_(g) + H₂O_(g)

Explanation; (a)

Correct option is a.

[Product] = [CH₃OH][H₂O] = is written in numerator (coefficient becomes power of concentration)

[Reactant] = [CO₂] [H₂]³= is written in denominator (coefficient becomes power of concentration)

70. The reaction A_(g) ⇌ B_(g) has a K value of 4.1 x 10² . At equilibrium, which of the following would be true?

(a) [A] = [B]

(b) [A] > [B]

(d) Both a and b

Explanation; (c)

A high value of K_c (K >> 1) is suggestive of a high concentration of products and vice-versa. Correct option is c

71. Phosphorus reacts with chlorine according to the following equation:

P_4(s) + 6Cl_2(g) ⇌ 4PCl_3(g)

What is the equilibrium constant, K_c, for the reaction?

Explanation; (c)

Concentration of pure liquid or pure solid does not appear in K_c expression. Correct option is c

72. For a reaction of the type; A_(s)+ 2B_(g)⇌ C_(g); an equilibrium mixture consist of 3.0 moles of A, 0.80 moles of B and 0.40 moles of C in a 2.00 L flask. What is the value of Kc for this reaction?

(a) 5.0 x 10^-1

(b) 8.3 x 10^-1

(d) 1.7 x 10^-1

Explanation; (c)

73. What is the equilibrium expression for the following reaction?

CuSO_4(s) + 5H₂O_(g) ⇌ CuSO₄.5H₂O_(s)

Explanation; (d)

Concentration of pure liquid or pure solid does not appear in K_c expression. Correct option is d

74. In the lime kiln, the reaction; CaCO₃ → CaO + CO₂ goes to completion reaction because;

(a) of high temperature

(b) CaO is more stable than CaCO₃

(d) CaO is not dissociated

Explanation; (c)

The escape of CO₂ from the reaction mixture favours forward reaction.

75. For a chemical reaction mA + nB ⇌ cC + pD, K_c expression is written as:

Explanation; (b)

The stoichiometric coefficients of balanced equation becomes power of the concentration.

76. For a reaction 3A + 2B ⇌ C, the K_c expression is written as:

Explanation; (b)

The stoichiometric coefficients of balanced equation becomes power of the concentration.

77. Active masses of the substance represent

(a) Concentration in mole/cm³

(b) Concentration in mole/m³

(d) Concentration in mole/ml

Explanation; (c)

Active mass represent amount of substance. It is generally expressed in terms of molar concentration (mol dm^‒3OR mol L^‒1). It is represented by [ ] = M = C = no of moles of substance per dm³