Chapter No.1: Chemical Equilibrium -Chemistry For Class X (2022 and Onward) - Multiple Choice Questions, Fill in the blanks, Concept Diagram

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Chemical Equilibrium
MULTIPLE CHOICE QUESTIONS (MCQs)

Tick the correct answer from the following:
1. Which one of the following statements is false about dynamic equilibrium?

• It takes place in a close container
• Concentration of reactant and products are not changed
• Rate of forward reaction is equal to rate of reverse reaction
• Equilibrium cannot be disturbed by any external stress ✔

2. Consider the following reaction and indicate which of the following best describe equilibrium constant expression Kc.

4NH₃ + 5O₂ ⇌ 4NO + 6H₂O

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

• Doted lines
• Single arrow
• Double arrow ✔
• Double straight line

4. When the magnitude of Kc is small, indicates:

• Reaction mixture contain most of the reactant ✔
• Reaction mixture contain most of the product
• Reaction mixture contain almost equal amount of reactant and product
• Reaction goes to completion

5. For which system does the equilibrium constant, Kc has units of concentration.

• N_2(g) + 3H_2(g) ⇌ 2NH_3(g) ✔
• N_2(g) + 0_2(g) ⇌ 2NO
• H_2(g) +1_2(g) ⇌ 2HI_(g)
• CO_2(g) + H_3(g) ⇌ CO + H₂O_(l)

6. The unit of K_c for reaction N₂ + O₂ ⇌ 2NO

• mol dm^-3
• mol^-2dm⁶
• mol^-1dm³
• no unit ✔

7. The system is stable in equilibrium when:

• Qc = Kc ✔
• Qc > Kc
• Qc < K
• None of these

8. Qc can be defined as:

• ratio of product and reactants
• ratio of molar concentration of product and reactant at specific time ✔
• ratio of molar concentration of product and molar volume of reactant
• ratio of molar concentration of product and reactant raised to the power of coefficient

9. Which of the following represent backward reaction?

• (i) and (ii)
• (ii) and (iii)
• (ii) only
• (iii) only ✔

10. The value of Kc increases when:

• [Product] is less
• [Product] is more ✔
• [Reactant] is more
• [Reactant = product]

11. Which of these are reversible reactions?

• Condensation
• Evaporation
• Both 'a' & 'b' ✔
• None of them

12. Which one is not a reversible reaction?

• Evaporation
• Melting
• Freezing
• Combustion ✔

13. Which reactions are irreversible reactions?
(i) Condensation (ii) Combustion (iii) Melting (iv) Rusting

• (i) & (ii)
• (iii) & (iv)
• (ii) & (iv) ✔
• (i) & (iv)

14. Many physical and chemical changes are occurring in our surrounding which may be due to:

• chemical reaction ✔
• physical reaction
• Both 'a' & 'b'
• None of these

15. Equilibrium is a state in which:

• the forward reaction rate is more than the reverse reaction rate.
• the forward reaction rate is less than the reverse reaction rate.
• forward reaction rate and reverse reaction rate are equal. ✔
• forward reaction rate and reverse reaction rate become zero.

16. Conversion of ice into the water by melting and conversion of water into ice by freezing is an example of:

• chemical reaction
• reversible reaction ✔
• irreversible reaction
• None of them

17. A chemical reaction is a chemical change which involves:

• reactants
• products
• Both 'a' & 'b' ✔
• None of these

18. The direction of a reaction can be predicted by the type of arrow:

• doted lines
• single arrow ✔
• double arrow
• double straight line

19. A reversible reaction containing:

• one process
• two processes ✔
• three processes
• four processes

20. The reaction rate depends on the concentration of the:

• reactants ✔
• products
• temperature
• Both 'a' & 'b'

21. At the beginning the reaction:

• quantity of reactant is lower, and the rate of product formation is lower
• quantity of reactant is lower, and the rate of product formation is higher
• quantity of reactant is higher, and the rate of product formation is lower
• quantity of reactant is higher, and the rate of product formation is higher ✔

22. As the reactant amount decreases, the rate of reactant transformation:

• decreases ✔
• increases
• remains the same
• becomes zero

23. The state of dynamic equilibrium can be represented by:

• Rate of the forward reaction < Rate of the reverse reaction
• Rate of the forward reaction > Rate of the reverse reaction
• Rate of the forward reaction = Rate of the reverse reaction ✔
• Rate of the forward reaction - Rate of the reverse reaction = 0

24. In a reversible reaction, dynamic equilibrium is established:

• after the completion of reaction
• before the completion of reaction ✔
• it depends on the amount of reactants
• at any time

25. Which statement is TRUE for a forward reaction?

• It is always directed from right to left in a chemical reaction
• Product produces reactant
• Initially rate is fast but gradually slows down ✔
• All of them

26. Which statement is NOT true for reverse reaction?

• It is always directed from left to right in a chemical reaction ✔
• Product produce reactant (Reactants → Products)
• Initially rate is slow but gradually speeds up
• All of them

27. The rate at which a substance reacts is directly proportional to its:

• density
• concentration
• atomic mass
• active mass ✔

28. The rote of a reaction is directly proportional to the product of the active masses of the:

• products
• reacting substances ✔
• Both 'a' & 'b'
• None of them

29. Kc = :

• reactant x product
• ^reactant / _product
• ^product / _reactant ✔
• reactant = product

30. It is the single factor affecting the equilibrium constant's value.

• Density
• Pressure
• Temperature ✔
• Numbers of moles

31. Kc is independent of:

• reactant concentration
• Product concentration
• Both 'a' & 'b' ✔
• None of these

32. Kc varies with:

• temperature ✔
• reactant concentration
• product concentration
• densities

33. If Kc is larger than 1, the reaction is:

• in equilibrium
• reverse reaction
• forward reaction ✔
• None of them

34. The reaction is a reverse reaction, if Kc is:

• larger than 1
• less than 1 ✔
• equal to 1
• equal to 0

35. Which Statement is true if Q_c < K_c.

• increase in product concentration for equilibrium
• The forward reaction occurs, forming addition product
• Both 'a' & 'b' ✔
• None of these

36. If Q_c > K_c:

• There is increase in product concentration as the process reverses, forming more reactant.
• There is increase in product concentration as the process reverses, forming more product.
• There is decrease in product concentration as the process reverses, forming more product.
• There is decrease in product concentration as the process reverses, forming more reactant. ✔

37. If K_c is very small, then:

• reactions never finish ✔
• reactions are virtually complete
• reactions are Considered to be at equilibrium
• None of these

38. If K_c is very large, then:

• the concentration of reactants and products is almost same-
• the reaction has Maximum reactant concentration and minimum product concentration
• the reaction has maximum product concentration and minimum reactant concentration ✔
• None of them

39. This type of reaction is known as 'Forward reaction'.

• K_c is very small
• K_c is very large ✔
• K_c is neither very small nor very large
• K_c is equal to 0

40. These are the most important part of the atmosphere.

• oxygen & carbon dioxide
• nitrogen & oxygen ✔
• carbon dioxide & methane
• oxygen & ozone

FILL IN THE BLANKS:

1. Many physical and chemical changes are occurring in our surrounding which may be due to chemical reaction.
2. The chemical reactions may be reversible or irreversible.
3. The reversible reaction never goes to completion.
4. The state in which rate of forward reaction becomes equal to the rate of reverse reaction are known as equilibrium.
5. Chemical equilibrium always observed in reversible reactions.
6. In reversible reactions reactants and product inter convert into each other.
7. Reversible reactions proceed in either direction i,e forward and backward.
8. In dynamic equilibrium the rate of forward reaction is high, and rate of reverse reaction is slow in beginning.
9. Dynamic equilibrium can only be achieved in a closed container with fixed temperature.
10. According to law of mass action: "At any instant, the rate of a chemical reaction at a given temperature is directly proportional to the product of the active masses of the reactants at that instant."
11. K_c is equilibrium constant.
12. K_f is the rate constant for forward reaction.
13. K_r is the rate constant for reverse reaction.
14. An equilibrium constant K_c is used to show relationship between molar concentration of product and molar concentration of reactant.
15. As K_c is a ratio and usually has no unit.
16. K_c is independent of initial concentration of reactant and product.
17. K_c is temperature dependent.
18. The value of equilibrium constant, K_c tells us the extent of a reaction.
19. K_c also gives direction of reaction.
20. Q_c is known as reaction quotient.
21. Single headed arrow (→) used for irreversible reaction.
22. A double headed arrows (⇄) used for reversible reaction.
23. N_2(g) + 3H_2(g) → 2NH_3(g). is known as forward reaction or irreversible reaction.
24. N_2(g) + 3H_2(g) ← 2NH_3(g). is known as reversible reaction.
25. Equilibrium means a 'balance'.
26. Forward reaction is always directed from left to right in a chemical reaction.
27. Reverse reaction is always directed from right to left in a chemical reaction.
28. The concentration of reacting substance is called Active mass.
29. The unit of active mass is mol dm^-3.
30. The value of active mass is expresses in square brackets.
31. If K_c is larger than 1, the reaction is forward.
32. If K_c is less than 1, the reaction is reverse reaction.
33. Nitrogen and oxygen are 99% of the atmosphere and use to make chemicals.
34. Nitrogen of the atmosphere is used for preparation of ammonia.
35. Ammonia is used to prepare nitrogenous fertilizers.
36. Oxygen of the atmosphere is used for preparation of sulphur dioxide.
37. Sulphur dioxide is used to prepare sulphuric acid.

Elements With Symbols

• Cl ⇨Chlorine
• F ⇨ Flourine
• H ⇨ Hydrogen
• I ⇨ Iodine
• N ⇨ Nitrogen
• O ⇨ Oxygen
• S ⇨ Sulphur

Compounds With Formulas

• CO ⇨ Carbon monoxide
• CO₂ ⇨ Carbon dioxide
• COCl₂ ⇨ Carbonyl dichloride (Phosgene)
• HCl ⇨ Hydrochloric acid
• HI ⇨ Hydrogen iodide
• H₂O ⇨ Water
• H₂SO₄ ⇨ Sulphuric Acid
• Na₂CO₃ ⇨ Sodium carbonate
• NaHCO₃ ⇨ Sodium bicarbonate
• NH₃ ⇨ Ammonia
• NH₄Cl ⇨ Ammonium chloride
• NO ⇨ Nitric oxide
• NO₂ ⇨ Nitrogen dioxide
• SO₂ ⇨ Sulphur dioxide
• SO₃ ⇨ Sulphur trioxide