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JEE Main Chemistry: Chemical and Ionic Equilibrium Practice Questions

15 free multiple-choice questions on Chemical and Ionic Equilibrium for JEE Main Chemistry, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.

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  1. Q1. Which thermodynamic relationship links the change in enthalpy (ΔH) and the change in entropy (ΔS) to the change in Gibbs Free Energy (ΔG)?

    • AΔG = ΔH + TΔS
    • BΔS = ΔH - ΔG
    • CΔH = ΔG + TΔS
    • DΔG = ΔH - TΔS
    Show answer & explanation

    Correct answer: D — ΔG = ΔH - TΔS

    The fundamental equation linking these quantities is ΔG = ΔH - TΔS. This equation defines the relationship between enthalpy, entropy, and Gibbs Free Energy.

  2. Q2. Which thermodynamic quantity determines the spontaneity of a chemical reaction at constant temperature and pressure?

    • AEntropy (S)
    • BInternal Energy (U)
    • CEnthalpy (H)
    • DGibbs Free Energy (ΔG)
    Show answer & explanation

    Correct answer: D — Gibbs Free Energy (ΔG)

    The change in Gibbs Free Energy (ΔG) determines the spontaneity of a process. A negative ΔG indicates a spontaneous process, while a positive ΔG indicates a non-spontaneous process under those conditions.

  3. Q3. If the standard enthalpy change (ΔH°) is negative and the standard entropy change (ΔS°) is positive, what does this imply about the spontaneity of the reaction at standard conditions?

    • AThe reaction is non-spontaneous
    • BThe reaction is at equilibrium
    • CThe reaction is only spontaneous at high temperatures
    • DThe reaction is spontaneous
    Show answer & explanation

    Correct answer: D — The reaction is spontaneous

    Since ΔG° = ΔH° - TΔS°, if ΔH° is negative and ΔS° is positive, ΔG° will be negative (assuming T is not excessively large), indicating the reaction is spontaneous.

  4. Q4. For a reaction at equilibrium, if ΔG is negative, what can be concluded about the reaction?

    • AThe reaction is spontaneous
    • BThe reaction is non-spontaneous
    • CThe reaction is at mechanical equilibrium
    • DThe equilibrium constant K is zero
    Show answer & explanation

    Correct answer: A — The reaction is spontaneous

    A negative change in Gibbs Free Energy (ΔG < 0) signifies that the reaction is spontaneous (favorable) under the given conditions.

  5. Q5. The change in Gibbs Free Energy (ΔG°) for a reaction is related to the equilibrium constant (K) by which equation?

    • AΔG° = ΔH + TΔS
    • BΔG° = ΔH - TΔS
    • CΔG° = -RT / K
    • DΔG° = -RT ln K
    Show answer & explanation

    Correct answer: D — ΔG° = -RT ln K

    The relationship between the standard Gibbs Free Energy change (ΔG°) and the equilibrium constant (K) is given by the fundamental equation: ΔG° = -RT ln K.

  6. Q6. The actual change in Gibbs free energy (ΔG) for a reaction occurring under non-standard conditions is related to the standard Gibbs free energy change (ΔG°) and the reaction quotient (Q) by which equation?

    • AΔG = ΔG° / Q
    • BΔG = ΔH - TΔS
    • CΔG = ΔG° - RT ln Q
    • DΔG = ΔG° + RT ln Q
    Show answer & explanation

    Correct answer: D — ΔG = ΔG° + RT ln Q

    The relationship linking the actual Gibbs free energy change (ΔG) to the standard state change (ΔG°) and the reaction quotient (Q) is ΔG = ΔG° + RT ln Q. This equation allows calculation of free energy under non-standard conditions.

  7. Q7. The relationship between the standard Gibbs free energy change (ΔG°) and the equilibrium constant (K) is given by which equation?

    • AΔG° = ΔH + TΔS
    • BΔG° = -(ΔH - TΔS)
    • CΔG° = RT ln K
    • DΔG° = -RT ln K
    Show answer & explanation

    Correct answer: D — ΔG° = -RT ln K

    The fundamental thermodynamic relationship linking standard Gibbs free energy change and the equilibrium constant is ΔG° = -RT ln K.

  8. Q8. If the change in Gibbs free energy (ΔG) for a reaction is negative, what does this imply about the spontaneity of the reaction?

    • AThe reaction is endothermic
    • BThe reaction is spontaneous
    • CThe reaction is non-spontaneous
    • DThe reaction is at equilibrium
    Show answer & explanation

    Correct answer: B — The reaction is spontaneous

    A negative change in Gibbs free energy (ΔG < 0) indicates that the reaction is spontaneous (favorable) under the given conditions.

  9. Q9. In a reaction occurring at equilibrium, what does the value of ΔG represent?

    • AThe reaction quotient (Q).
    • BThe change in enthalpy of the system.
    • CThe driving force for the reaction.
    • DThe heat evolved during the reaction.
    Show answer & explanation

    Correct answer: C — The driving force for the reaction.

    At equilibrium, the change in Gibbs Free Energy (ΔG) is zero, meaning the net change in free energy for the system at equilibrium is zero, indicating no further net change can occur.

  10. Q10. If a chemical reaction has a positive change in enthalpy (ΔH) and a negative change in entropy (ΔS), what is the thermodynamic implication for the spontaneity of the reaction at constant temperature?

    • AThe reaction is spontaneous because ΔG must be positive.
    • BThe reaction is spontaneous because ΔH is positive.
    • CThe reaction is non-spontaneous because ΔH is positive.
    • DThe spontaneity depends solely on ΔS.
    Show answer & explanation

    Correct answer: C — The reaction is non-spontaneous because ΔH is positive.

    The spontaneity is determined by ΔG = ΔH - TΔS. If ΔH > 0 and ΔS > 0, the sign of ΔG depends on T. However, for a spontaneous process, ΔG must be negative. This option tests the understanding that ΔG governs spontaneity, not just ΔH or ΔS independently.

  11. Q11. For a chemical reaction occurring at equilibrium, what is the value of the Gibbs free energy change (ΔG)?

    • ADependent on temperature
    • BAlways negative
    • CAlways positive
    • DAlways zero
    Show answer & explanation

    Correct answer: B — Always negative

    At chemical equilibrium, the system is stable, meaning the change in Gibbs free energy (ΔG) for the overall process is zero.

  12. Q12. Which thermodynamic parameter is used to determine the spontaneity of a process at constant temperature and pressure?

    • AInternal Energy change (ΔU)
    • BEnthalpy change (ΔH)
    • CEntropy change (ΔS)
    • DGibbs Free Energy change (ΔG)
    Show answer & explanation

    Correct answer: D — Gibbs Free Energy change (ΔG)

    The change in Gibbs Free Energy (ΔG) is the criterion used to predict the spontaneity of a process under constant temperature and pressure.

  13. Q13. For a reversible reaction, if the Gibbs free energy change (ΔG) is zero, what is the state of the system?

    • AThe reaction is non-spontaneous.
    • BThe reaction is spontaneous.
    • CThe reaction is highly exothermic.
    • DThe system is at equilibrium.
    Show answer & explanation

    Correct answer: D — The system is at equilibrium.

    When the Gibbs free energy change (ΔG) for a process is zero, the system is at equilibrium, meaning the rates of the forward and reverse reactions are equal.

  14. Q14. If the standard Gibbs free energy change (ΔG°) for a reaction is zero, what does this imply about the equilibrium state of the reaction?

    • AThe reaction proceeds reversibly only at infinite temperature
    • BThe reaction is highly spontaneous
    • CThe reaction is non-spontaneous
    • DThe reaction is at equilibrium
    Show answer & explanation

    Correct answer: D — The reaction is at equilibrium

    When ΔG° = 0, it means that the reaction is at equilibrium under the specified standard conditions.

  15. Q15. Which thermodynamic quantity represents the maximum potential non-expansion work obtainable from a system at constant temperature and pressure?

    • AEnthalpy (H)
    • BInternal Energy (U)
    • CGibbs Free Energy (G)
    • DHelmholtz Free Energy (A)
    Show answer & explanation

    Correct answer: C — Gibbs Free Energy (G)

    Gibbs Free Energy (G) is the thermodynamic potential that measures the maximum non-expansion work that can be extracted from a system at constant temperature and pressure, making it crucial for determining spontaneity in chemical reactions.

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