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Equilibrium WBCHSE Class 11 MCQ & Practice Questions

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

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Equilibrium Revision Guide for WBCHSE 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 WBCHSE 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 WBCHSE 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.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

1. Le Chatelier's principle predicts the response of equilibrium to:

  • A. Only nuclear changes
  • B. A disturbance in conditions
  • C. Only catalysts
  • D. Only light
Answer: B
Explanation: The system shifts so as to oppose an imposed change.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

2. Increasing concentration of a reactant generally shifts equilibrium:

  • A. Toward products
  • B. Toward reactants
  • C. Nowhere under any condition
  • D. Only if catalyst exists
Answer: A
Explanation: The system consumes part of the added reactant.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

3. Removing a product from an equilibrium mixture generally shifts equilibrium:

  • A. Toward reactants
  • B. Does not shift
  • C. Stops reaction
  • D. Toward products
Answer: D
Explanation: More product forms to oppose its removal.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

4. The equilibrium constant Kc is written using:

  • A. Equilibrium molar concentrations
  • B. Initial concentrations only
  • C. Reaction rates
  • D. Catalyst concentrations
Answer: A
Explanation: Kc is defined from equilibrium concentrations raised to stoichiometric powers.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

5. For aA+bB⇌cC+dD, Kc equals:

  • A. [A]^a[B]^b/[C]^c[D]^d
  • B. [C+D]/[A+B]
  • C. a+b+c+d
  • D. [C]^c[D]^d/[A]^a[B]^b
Answer: D
Explanation: Products appear in the numerator and reactants in the denominator.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

6. For gaseous equilibrium, Kp is expressed using:

  • A. Densities only
  • B. Partial pressures
  • C. Molar masses
  • D. Total mass only
Answer: B
Explanation: Kp is defined in terms of equilibrium partial pressures.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

7. For gaseous reactions, Kp and Kc are related by:

  • A. Kp=Kc(RT)^Δn
  • B. Kp=Kc/RT always
  • C. Kp=Kc+RT
  • D. Kp=1/Kc
Answer: A
Explanation: Δn is gaseous product moles minus gaseous reactant moles.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

8. If Δn=0 for a gaseous reaction, then:

  • A. Kp>Kc always
  • B. Kp<Kc always
  • C. Kp=0
  • D. Kp=Kc
Answer: D
Explanation: The factor (RT)^Δn becomes unity.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

9. The reaction quotient Q has the same algebraic form as:

  • A. The Henderson equation only
  • B. The equilibrium constant expression
  • C. The rate law necessarily
  • D. The ideal gas law
Answer: B
Explanation: Q uses current rather than necessarily equilibrium activities/concentrations.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

10. If Q>K, the reaction tends to proceed:

  • A. Forward
  • B. Neither
  • C. Only at zero temperature
  • D. In reverse direction
Answer: D
Explanation: Products are excessive relative to equilibrium and are consumed.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

11. If Q=K, the system is:

  • A. Necessarily all products
  • B. Necessarily all reactants
  • C. At equilibrium
  • D. Completely reacted
Answer: C
Explanation: Equality of Q and K is the equilibrium criterion.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

12. A conjugate acid-base pair differs by:

  • A. One oxygen atom always
  • B. One proton
  • C. One neutron
  • D. Two electrons
Answer: B
Explanation: Proton transfer interconverts conjugate acid-base partners.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

13. At 25°C, pH+pOH is approximately:

  • A. 7
  • B. 1
  • C. 0
  • D. 14
Answer: D
Explanation: This follows from pKw≈14.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

14. At dynamic equilibrium, the forward and reverse reaction rates are:

  • A. Increasing continuously
  • B. Unrelated
  • C. Equal
  • D. Zero
Answer: C
Explanation: At equilibrium the opposing reaction rates are equal.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

15. For a reversible reaction at equilibrium, macroscopic concentrations are:

  • A. Changing rapidly
  • B. Constant with time
  • C. All zero
  • D. Always equal to one another
Answer: B
Explanation: Equal forward and reverse rates keep concentrations constant.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

16. Pure solids are omitted from heterogeneous equilibrium expressions because their:

  • A. Concentrations are infinite
  • B. Moles never change
  • C. Activities are effectively constant
  • D. Masses are zero
Answer: C
Explanation: The activity of a pure solid is treated as unity.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

17. A very large equilibrium constant generally indicates:

  • A. No reaction occurs
  • B. Catalyst is absent
  • C. Products are strongly favoured
  • D. Reactants are strongly favoured
Answer: C
Explanation: Large K means the equilibrium composition lies mainly toward products.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

18. A very small equilibrium constant generally indicates:

  • A. Reaction is irreversible
  • B. Reactants are favoured
  • C. Products are favoured
  • D. Equal amounts always
Answer: B
Explanation: Small K means relatively little product exists at equilibrium.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

19. If a reaction equation is reversed, its new equilibrium constant is:

  • A. 1/K
  • B. K²
  • C. 2K
  • D. K
Answer: A
Explanation: Reversing numerator and denominator reciprocates the constant.

WBCHSE Class 11 Chemistry · Equilibrium · Very Hard

20. If all coefficients of a reaction are multiplied by 2, the new equilibrium constant is:

  • A. 2K
  • B. K/2
  • C. sqrt(K)
  • D. K²
Answer: D
Explanation: Stoichiometric powers double, so the equilibrium constant is squared.

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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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