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Equilibrium CBSE Class 11 MCQ & Practice Questions

Practice Equilibrium MCQs for CBSE Class 11 Chemistry with answers, explanations, chapter revision and related ChemNexa mock tests.

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Equilibrium Revision Guide for CBSE Class 11 Chemistry

Equilibrium covers reversible chemical processes and the quantitative relationship between reactants and products at equilibrium. It also includes acid-base, ionic and solubility equilibria in many syllabi.

For CBSE Class 11 Chemistry, build confidence with equilibrium constants, reaction quotient, Le Chatelier principle, pH calculations, buffer concepts and solubility product.

Important Topics

  • Dynamic chemical equilibrium
  • Kc, Kp and reaction quotient
  • Le Chatelier principle
  • Acid-base equilibrium and pH
  • Buffer solutions
  • Solubility product and common-ion effect

Important Formulae & Relationships

  • Kp = Kc(RT)^Δn
  • pH = −log[H+]
  • pOH = −log[OH−]
  • pH + pOH = 14 at 25°C
  • Ka × Kb = Kw for a conjugate pair

Use formulas only after checking the required units, sign convention and assumptions for the question.

What to practise in Equilibrium

Concept Revision

Revise definitions, principles, equations, trends and core ideas from Equilibrium before attempting MCQs.

Exam-style MCQs

Use chapter-focused multiple-choice practice to improve accuracy, recall and application for CBSE Class 11 Chemistry.

Performance Practice

Attempt ChemNexa tests, review results and return to weak areas for another round of targeted revision.

Top 20 Equilibrium MCQs with Answers

These public questions are selected from the exact Equilibrium chapter, screened for topic relevance and deduplicated so repeated versions of the same MCQ are not shown publicly. Use them for quick revision, then sign in to attempt the complete test experience with more questions, results and performance review.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

1. For an exothermic forward reaction, increasing temperature shifts equilibrium:

  • A. Toward products
  • B. Toward reactants
  • C. Nowhere
  • D. Only if a catalyst is present
Answer: B
Explanation: Heat behaves like a product in an exothermic reaction, so adding heat favours the reverse direction.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

2. The reaction quotient Qc predicts direction because:

  • A. Qc always equals zero
  • B. Qc is compared with Kc
  • C. Qc changes the value of Kc
  • D. Qc is independent of composition
Answer: B
Explanation: If Qc<Kc, the reaction proceeds forward; if Qc>Kc, it proceeds in reverse.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

3. If Qc < Kc, the reaction proceeds:

  • A. In the forward direction
  • B. In the reverse direction
  • C. Not at all
  • D. Only after cooling
Answer: A
Explanation: More products must form for Qc to increase to Kc.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

4. The conjugate base of H₂CO₃ is:

  • A. CO₃²⁻
  • B. HCO₃⁻
  • C. H₃CO₃⁺
  • D. OH⁻
Answer: B
Explanation: Loss of one proton from H₂CO₃ gives HCO₃⁻.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

5. The common-ion effect generally:

  • A. Increases ionisation of a weak electrolyte
  • B. Suppresses ionisation of a weak electrolyte
  • C. Changes temperature
  • D. Makes every salt insoluble
Answer: B
Explanation: Adding a common ion shifts the ionisation equilibrium toward the unionised form.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

6. For a sparingly soluble salt AB(s) ⇌ A⁺ + B⁻, Ksp equals:

  • A. [AB]
  • B. [A⁺][B⁻]
  • C. [A⁺]+[B⁻]
  • D. 1/[A⁺][B⁻]
Answer: B
Explanation: The solubility product is the product of equilibrium ion concentrations.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

7. For aA + bB ⇌ cC + dD, the equilibrium constant Kc is:

  • A. [A]^a[B]^b/[C]^c[D]^d
  • B. [C]^c[D]^d/[A]^a[B]^b
  • C. [C+D]/[A+B]
  • D. [A+B]/[C+D]
Answer: B
Explanation: The equilibrium constant is the product concentration term divided by the reactant concentration term, each raised to its stoichiometric coefficient.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

8. For N₂(g) + 3H₂(g) ⇌ 2NH₃(g), the relation between Kp and Kc is:

  • A. Kp = Kc(RT)²
  • B. Kp = Kc(RT)⁻²
  • C. Kp = KcRT
  • D. Kp = Kc
Answer: B
Explanation: Δn = 2 − 4 = −2, so Kp = Kc(RT)^−2.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

9. If Kc is much greater than 1, equilibrium generally favours:

  • A. Reactants
  • B. Products
  • C. Neither side
  • D. Only the catalyst
Answer: B
Explanation: A large equilibrium constant indicates that products predominate at equilibrium.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

10. The conjugate acid of NH₃ is:

  • A. NH₂⁻
  • B. NH₄⁺
  • C. N₂H₄
  • D. NH₄OH
Answer: B
Explanation: NH₃ accepts a proton to form NH₄⁺.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

11. A buffer solution resists changes in:

  • A. Temperature
  • B. Pressure
  • C. pH
  • D. Volume only
Answer: C
Explanation: Buffers consume added H⁺ or OH⁻ and minimise pH change.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

12. At dynamic equilibrium in a reversible reaction:

  • A. Both reactions stop
  • B. Forward and reverse reaction rates are equal
  • C. Reactant and product concentrations are necessarily equal
  • D. Only the reverse reaction continues
Answer: B
Explanation: Dynamic equilibrium means that forward and reverse reactions continue at equal rates.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

13. Pure solids are omitted from an equilibrium-constant expression because:

  • A. They never react
  • B. Their activity is effectively constant
  • C. Their concentration is zero
  • D. They have no mass
Answer: B
Explanation: The activity of a pure solid is constant and incorporated into the equilibrium constant.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

14. A catalyst added to an equilibrium system:

  • A. Changes Kc
  • B. Shifts equilibrium toward products
  • C. Speeds attainment of equilibrium without changing its position
  • D. Stops the reverse reaction
Answer: C
Explanation: A catalyst lowers activation energies of both directions equally and does not alter equilibrium composition.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

15. For N₂ + 3H₂ ⇌ 2NH₃, increasing pressure shifts equilibrium toward:

  • A. N₂ and H₂
  • B. NH₃
  • C. No change
  • D. The side with more gas molecules
Answer: B
Explanation: Higher pressure favours the side with fewer gaseous moles: two moles of NH₃ instead of four reactant moles.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

16. Removing a product from an equilibrium mixture generally:

  • A. Shifts equilibrium toward reactants
  • B. Shifts equilibrium toward products
  • C. Changes Kc
  • D. Stops both reactions
Answer: B
Explanation: The system responds by forming more product to oppose its removal.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

17. At 25°C, a neutral aqueous solution has:

  • A. pH 0
  • B. pH 7
  • C. pH 14
  • D. pOH 0
Answer: B
Explanation: In neutral water, [H₃O⁺]=[OH⁻]=10⁻⁷ M, giving pH 7.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

18. The pH of 1.0×10⁻³ M HCl is approximately:

  • A. 1
  • B. 3
  • C. 7
  • D. 11
Answer: B
Explanation: HCl is a strong acid, so [H₃O⁺]=10⁻³ M and pH=3.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

19. The pOH of 1.0×10⁻⁴ M NaOH at 25°C is:

  • A. 4
  • B. 10
  • C. 7
  • D. 14
Answer: A
Explanation: NaOH is a strong base, so [OH⁻]=10⁻⁴ M and pOH=4.

CBSE Class 11 Chemistry · Equilibrium · Very Very Hard

20. A weak acid has Ka = 1.0×10⁻⁵. Compared with an acid having Ka = 1.0×10⁻³, it is:

  • A. Stronger
  • B. Weaker
  • C. Equally strong
  • D. A strong base
Answer: B
Explanation: A smaller Ka means less ionisation and therefore a weaker acid.

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Equilibrium Practice Tests

Equilibrium Frequently Asked Questions

What is the difference between Q and K?

The reaction quotient Q uses the current composition; K describes the equilibrium composition at a fixed temperature. Comparing Q with K predicts the direction of shift.

Does a catalyst change the equilibrium constant?

No. A catalyst changes the rate at which equilibrium is reached but does not change the equilibrium constant at a given temperature.

How should I practise ionic equilibrium?

Work systematically with species, approximations, charge or mass balance when needed, and verify that the final concentration or pH is chemically reasonable.

Continue with another chapter to build connected concepts and strengthen your overall Chemistry preparation.

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