Exam-Style Mock Test | Class 11 Chemistry: Equilibrium

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Quiz: Equilibrium – Certificate Challenge
Total questions: 453
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Certificate pass score: 70%
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Equilibrium – Progressive Test

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1 / 50

1. For the same pure liquid in a closed vessel, vapour pressure at equilibrium is higher at than at because

a) higher temperature helps molecules escape the liquid

b) higher temperature removes all vapour molecules from the vessel

c) condensation becomes impossible at

d) temperature changes the chemical identity of every liquid molecule

2 / 50

2. For , the relationship between and is

3 / 50

3. For the general equilibrium , the correct concentration equilibrium constant expression is

4 / 50

4. A table gives values at .

Solution
P
Q
R
S

The most basic solution is

a) S

b) P

c) Q

d) R

5 / 50

5. The table lists four descriptions of physical systems.

System	Description
P	Water in an open dish slowly evaporates into the room
Q	Ice and water coexist at the melting point under fixed pressure
R	Dry salt is heated until it decomposes
S	Gas escapes continuously from an uncorked soda bottle

The system best representing physical equilibrium is

a) Q

b) R

c) P

d) S

6 / 50

6. In a reversible reaction, the phrase “microscopic reaction continues” means that

a) atoms are not conserved during the molecular changes

b) molecules keep changing between forms

c) the reaction mixture must become invisible

d) the temperature must keep increasing

7 / 50

7. A rate-time record for a reversible reaction is given below.

Stage	Forward rate	Reverse rate
P	High	Nearly zero
Q	Decreasing	Increasing
R	Equal to reverse rate	Equal to forward rate

The stage representing dynamic equilibrium is

a) P

b) none of the stages

c) Q

d) R

8 / 50

8. A catalyst is added to a reversible reaction already at equilibrium. The catalyst will

a) leave the equilibrium composition unchanged

b) increase the equilibrium constant

c) decrease the equilibrium constant

d) change the equilibrium composition toward products

9 / 50

9. Assertion: A catalyst does not change the equilibrium composition of a reversible reaction.
Reason: A catalyst changes the rates of both forward and reverse reactions without changing the equilibrium condition.

a) Both assertion and reason are true, and the reason explains the assertion

b) Both assertion and reason are true, but the reason does not explain the assertion

c) The assertion is false, but the reason is true

d) The assertion is true, but the reason is false

10 / 50

10. For , if the molar solubility is , the correct relation between and is

11 / 50

11. The idea “equilibrium is static because no visible change occurs” is weak because

a) equilibrium can occur only in gases

b) visible constancy can hide opposite processes

c) equilibrium requires the temperature to become

d) equilibrium always produces equal masses of reactants and products

12 / 50

12. A reaction is written as . If concentration is measured in , the unit of for this reaction is

b) no unit by cancellation

13 / 50

13. A salt has . In one solution, and . The best conclusion is

a) precipitation occurs because one ion concentration is small

b) precipitation does not occur because

c) precipitation occurs because

d) the solution is exactly saturated

14 / 50

14. A sample of is mixed with of . The final solution is

a) neutral, because both solutions have the same molarity

b) acidic, because excess remains

c) basic, because excess remains

d) a buffer, because acid and base are mixed

15 / 50

15. A reaction is written as with . A second source writes the same change as . The statement “the first source shows a more product-favoured reaction because ” is weak if the second source has because

a) equilibrium constants are independent of coefficients

b) the two constants refer to differently scaled equations

c) product-favoured reactions never have

d) the second source must have used pressure instead of concentration

16 / 50

16. For , of is taken in a vessel. At equilibrium, total pressure is and . The degree of dissociation is closest to

17 / 50

17. For , an equilibrium mixture has , , , and . Extra is added suddenly so that becomes before any shift occurs. The initial shift is

a) reverse

b) impossible to decide without changing

c) no net shift

d) forward

18 / 50

18. A buffer contains of and of . If , and then of strong acid is added, with volume change neglected, , and , the final is closest to

19 / 50

19. A table summarizes four equilibrium disturbances.

Case	System	Disturbance	Expected response
P	Weak acid	Add	Ionization suppressed
Q		Add	Solubility decreases
R		Increase volume	Shifts toward
S	Exothermic forward reaction	Increase temperature	Shifts forward

The row that needs correction is

a) S

b) P

c) Q

d) R

20 / 50

20. A saturated solution of a sparingly soluble salt contains undissolved solid at the bottom. The equilibrium is dynamic because

a) no ions are present in solution

b) all dissolved ions lose their charges

c) dissolution and precipitation balance

d) the solid has stopped interacting with water

21 / 50

21. A comparison of two dissociation equilibria is made:

Case	Equilibrium	Initial amount	Total moles at equilibrium
P
Q
R
S

The two rows with suitable total mole expressions are

a) Q and R

b) P and Q

c) R and S

d) P and S

22 / 50

22. A weak acid approximation gives for a acid. The percent ionization is

23 / 50

23. A graph of vapour pressure of a pure liquid against time in a closed vessel at constant temperature first rises and then becomes horizontal. The horizontal part represents

a) chemical conversion of vapour into another substance

b) disappearance of all liquid

c) complete stopping of evaporation

d) constant vapour pressure at equilibrium

24 / 50

24. The unit of for , when concentration is reported in , is

d) no unit because every is unitless

25 / 50

25. A reversible chemical reaction is represented as . The reverse reaction is

26 / 50

26. A solution at has . Its is

27 / 50

27. In a reversible reaction graph, the strongest evidence for equilibrium is

a) all concentration curves becoming constant with time

b) the forward curve being drawn above the reverse curve forever

c) a single high concentration of product

d) the product curve crossing the reactant curve

28 / 50

28. Acid-base indicators work because their colour depends on

a) the total mass of the indicator bottle

b) the number of glass rods used for stirring

c) the equilibrium between differently coloured indicator forms

d) the pressure above the solution only

29 / 50

29. A weak acid is weak mainly because

a) it ionizes only partially in water

b) its solution must always have very low concentration

c) it cannot conduct electricity at all

d) it contains no hydrogen atoms

30 / 50

30. For the equilibrium , , and initially , . Using the small- approximation, the approximate value of in , is

31 / 50

31. The charge notation in and indicates that

a) has charge and has charge

b) both ions are neutral because they contain several atoms

c) the superscript only counts atoms, not charge

d) has charge and has charge

32 / 50

32. For , an equilibrium mixture has and . The equilibrium concentration of is

33 / 50

33. A solution of is basic because

a) sodium acetate behaves as a strong acid salt

b) forms completely in water

c) acetate ion is the conjugate acid of a strong base

d) acetate ion produces by hydrolysis

34 / 50

34. For , the solubility product expression is

35 / 50

35. The relation defining is

36 / 50

36. For , at . Using , is closest to

37 / 50

37. The quantity that most directly tells how much solute is present in a given volume of solution is

a) reaction rate

b) temperature

c) concentration

d) pressure

38 / 50

38. A saturated solution of is treated with acid. Its solubility increases mainly because

a) acid converts into a gas

b) acid increases at the same temperature

c) acid removes the solid from the equilibrium expression by changing notation only

d) acid consumes , shifting the dissolution equilibrium to the right

39 / 50

39. Equal volumes of and are mixed. If , the mixture is

a) unsaturated, so no precipitates

b) saturated exactly at equilibrium

c) supersaturated, so precipitates

d) impossible to judge because equal volumes are used

40 / 50

40. In the Haber process, , high pressure favours ammonia formation because

a) the product side has more gaseous moles

b) pressure changes the formula of ammonia

c) nitrogen is a solid at reaction conditions

d) the product side has fewer gaseous moles

41 / 50

41. A mixture has for a reversible reaction at fixed temperature. The best conclusion is that

a) the system is at equilibrium

b) the reverse reaction is faster than the forward reaction

c) the forward reaction is faster than the reverse reaction

d) all concentrations must be equal

42 / 50

42. A reversible reaction has a very large value of . The most reasonable description of its extent is that

a) the reaction mixture is not dynamic

b) no reactant molecules can remain at equilibrium

c) products are strongly favoured at equilibrium

d) the reverse reaction is impossible

43 / 50

43. At the melting point of a pure solid at a given pressure, solid-liquid equilibrium means that

a) only melting occurs and freezing is impossible

b) only freezing occurs and melting is impossible

c) melting and freezing occur at equal rates

d) the solid and liquid must have equal masses

44 / 50

44. In a closed vessel containing liquid water and its vapour, the measurable property that becomes constant at fixed temperature is

a) the chemical formula of water

b) the molar mass of water

c) the colour of water

d) the vapour pressure of water

45 / 50

45. A solution contains and . Silver ion is added gradually. Given and , the first precipitate is

c) neither because is common to both

d) both at the same

46 / 50

46. The basic buffer equation is most suitably written as

47 / 50

47. An acidic buffer contains and . If and , the is closest to

48 / 50

48. For , the initial concentration of is , and no is present. If , then is

49 / 50

49. For , . The equilibrium constant for is

50 / 50

50. Phase labels in an equilibrium equation are useful because they help decide

a) whether the reaction has stopped at equilibrium

b) whether reactants and products must have equal masses

c) homogeneous or heterogeneous classification

d) whether all coefficients must be ignored

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Equilibrium Mock Test – Class 11 Chemistry

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Equilibrium – Progressive Test

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