Equilibrium Important Questions.

Master Equilibrium with AI-powered practice. Our adaptive tutor identifies your gaps and provides step-by-step explanations for every topic in this chapter.

Practice questions covering all these NCERT topics — with AI explanations for each concept.

Practice these Equilibrium questions for Class 11 Chemistry, each with the correct answer and a step-by-step explanation. Sign up free to practice all 72+ questions with adaptive difficulty.

1. Q1Medium

   What is the primary characteristic of a system at dynamic equilibrium?

   • A.Forward reaction stops while the reverse reaction continues.
   • B.The concentration of reactants becomes zero.
   • C.The rate of the forward reaction equals the rate of the reverse reaction.
   • D.The reaction mixture changes composition over time.
   Answer: The rate of the forward reaction equals the rate of the reverse reaction.

   Explanation: Dynamic equilibrium represents a state where both forward and reverse processes are continuously occurring, maintaining constant concentrations of reactants and products over time. This concept is central to understanding many chemical reactions.

2. Q2Medium

   What does the equilibrium constant, Kc, represent?

   • A.The rate of the forward reaction.
   • B.The total pressure of the reaction system.
   • C.The ratio of product concentrations to reactant concentrations at equilibrium.
   • D.The change in Gibbs free energy during the reaction.
   Answer: The ratio of product concentrations to reactant concentrations at equilibrium.

   Explanation: The equilibrium constant, Kc, quantifies the extent to which a reaction proceeds to products at equilibrium. It is a dimensionless value that can help predict the direction of a reaction based on initial concentrations.

3. Q3Medium

   According to Le Chatelier's Principle, how will increasing temperature affect an endothermic reaction at equilibrium?

   • A.The equilibrium will shift to the reverse direction.
   • B.The equilibrium position remains unchanged.
   • C.The equilibrium will shift in the forward direction to produce more products.
   • D.The equilibrium constants (K) will decrease.
   Answer: The equilibrium will shift in the forward direction to produce more products.

   Explanation: Le Chatelier's Principle states that if a system at equilibrium is subjected to a change, the system adjusts to counteract the change. For an endothermic reaction, increasing temperature favors the forward reaction to absorb heat and relieve the stress of the added heat.

4. Q4Medium

   What is the role of a buffer solution?

   • A.Increasing the solubility of a non-electrolyte.
   • B.Accelerating the rate of a reaction significantly.
   • C.Maintaining a relatively constant pH in a solution.
   • D.Decomposing into its constituent elements.
   Answer: Maintaining a relatively constant pH in a solution.

   Explanation: A buffer solution resists changes in pH by neutralizing added acids or bases. It usually consists of a weak acid and its conjugate base or a weak base and its conjugate acid, thus maintaining equilibrium pH levels within biological and industrial systems.

5. Q5Medium

   Which of the following processes is an example of physical equilibrium?

   • A.The dissociation of a weak acid in water.
   • B.The combination of hydrogen and oxygen to form water.
   • C.The vapor phase of water in equilibrium with liquid water inside a closed container.
   • D.The conversion of carbon dioxide to calcium carbonate.
   Answer: The vapor phase of water in equilibrium with liquid water inside a closed container.

   Explanation: Physical equilibrium refers to the state of balance between phases of a substance. Here, the rates of evaporation and condensation of water are equal, resulting in a dynamic equilibrium between liquid and vapor phases.

6. Q6Medium

   What type of acid-base theory defines acids as proton donators and bases as proton acceptors?

   • A.Arrhenius theory
   • B.Lewis theory
   • C.Brønsted-Lowry theory
   • D.Solvation theory
   Answer: Brønsted-Lowry theory

   Explanation: The Brønsted-Lowry theory defines acids and bases in terms of proton (H+) transfer. This theory is more comprehensive than the Arrhenius theory as it applies to reactions in non-aqueous solutions and includes conjugate acid-base pairs.

7. Q7Medium

   Which equilibrium constant, Kp, specifically considers the partial pressures of gases?

   • A.Equilibrium constant in terms of molar concentrations, Kc.
   • B.Equilibrium constant related to the reaction quotient, Qc.
   • C.Equilibrium constant in terms of partial pressures, Kp.
   • D.Ionic strength equilibrium constant.
   Answer: Equilibrium constant in terms of partial pressures, Kp.

   Explanation: Kp is an equilibrium constant that uses partial pressures for gaseous species. It is particularly useful for gas-phase reactions and can be related to Kc through the ideal gas law, PV = nRT.

8. Q8Medium

   In the Haber process, how is equilibrium shifted to maximize ammonia production?

   • A.By lowering the temperature.
   • B.By increasing the surface area of the catalyst.
   • C.By increasing pressure and removing ammonia as it forms.
   • D.By using a higher concentration of nitrogen.
   Answer: By increasing pressure and removing ammonia as it forms.

   Explanation: The Haber process involves producing ammonia from nitrogen and hydrogen gases. Increasing pressure shifts the equilibrium towards the products, favoring ammonia formation, while removing ammonia drives the reaction forward to maintain equilibrium.

9. Q9Medium

   What happens to the degree of ionization of a weak acid when a common ion is added?

   • A.It increases.
   • B.It remains unchanged.
   • C.It decreases.
   • D.It becomes infinite.
   Answer: It decreases.

   Explanation: The common ion effect shifts the equilibrium of a weak acid dissociation towards the reactant side due to the presence of an added ion that is already part of the equilibrium expression, thus reducing ionization.

10. Q10Medium

    What is used to describe the hydrogen ion concentration in a solution?

    • A.Molarity.
    • B.pKa scale.
    • C.pH scale.
    • D.pKw scale.
    Answer: pH scale.

    Explanation: The pH scale is a logarithmic measure of the hydrogen ion concentration in a solution. It ranges from 0 to 14, where lower values indicate higher acidity and higher values indicate higher basicity.

11. Q11Medium

    What does the reaction quotient, Qc, represent?

    • A.The equilibrium constant at standard conditions.
    • B.The specific heat of the reaction.
    • C.A measure used to determine the direction a reaction will proceed to reach equilibrium.
    • D.The change in enthalpy of the reaction.
    Answer: A measure used to determine the direction a reaction will proceed to reach equilibrium.

    Explanation: The reaction quotient, Qc, is similar to the equilibrium constant but is used at any point in the reaction, not necessarily at equilibrium. It helps predict if a reaction will proceed forward or backward to reach equilibrium.

12. Q12Medium

    Which principle is used to explain how industrial reactions can be optimized for higher product yield?

    • A.Hess's Law.
    • B.Law of Conservation of Mass.
    • C.Le Chatelier's Principle.
    • D.Avogadro's Law.
    Answer: Le Chatelier's Principle.

    Explanation: Le Chatelier's Principle helps predict how changes in conditions, such as temperature, pressure, and concentration, affect the position of chemical equilibrium, guiding industrial processes to maximize desired product yield.

Why practice Equilibrium on AskAide?