NEET Chemistry: Thermodynamics & Equilibrium MCQs with Solutions – PDF Download
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Boost your NEET Chemistry preparation with our comprehensive set of Thermodynamics and Equilibrium MCQs designed specifically for NEET 2025 aspirants. This free PDF download includes multiple-choice questions with detailed solutions, covering important concepts, formulas, and problem-solving techniques. Ideal for last-minute revision and self-assessment, this resource aligns with the latest NEET syllabus and exam pattern. Strengthen your grasp on key topics like the First Law of Thermodynamics, Gibbs Free Energy, Chemical Equilibrium, Le Chatelier’s Principle, and more.
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✅ Topic-wise MCQs with Answers
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NEET Chemistry: Thermodynamics & Equilibrium MCQs with Solutions – PDF Download
Are you preparing for NEET and looking for high-quality Chemistry MCQs on Thermodynamics and Equilibrium? You’ve come to the right place! This resource provides a comprehensive set of multiple-choice questions (MCQs) with detailed solutions to help you master these crucial topics in your NEET Chemistry syllabus.
Why Practice Thermodynamics and Equilibrium MCQs for NEET?
Thermodynamics and Chemical Equilibrium are vital topics in the NEET Chemistry curriculum. Questions from these chapters often test your conceptual clarity and problem-solving skills. Practicing MCQs allows you to:
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Understand key concepts like laws of thermodynamics, enthalpy, entropy, Gibbs free energy, and equilibrium constants.
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Improve speed and accuracy for the NEET exam.
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Identify weak areas and strengthen your knowledge.
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Get familiar with the type and pattern of questions asked in NEET.
Important Topics Covered in This PDF
Our NEET Chemistry Thermodynamics & Equilibrium MCQs PDF includes questions on:
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First Law of Thermodynamics
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Enthalpy and Internal Energy
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Hess’s Law
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Second Law of Thermodynamics
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Entropy and Gibbs Free Energy
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Chemical Equilibrium Basics
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Le Chatelier’s Principle
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Equilibrium Constant (Kc, Kp)
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Factors Affecting Equilibrium
Sample MCQs with Solutions
Q1. Which of the following is a state function?
a) Work
b) Heat
c) Enthalpy
d) Path
Answer: c) Enthalpy
Explanation: Enthalpy is a state function because it depends only on the state of the system, not on the path taken.
Q2. At equilibrium, the value of the reaction quotient (Q) is:
a) Less than K
b) Greater than K
c) Equal to K
d) Zero
Answer: c) Equal to K
Explanation: At equilibrium, the reaction quotient Q equals the equilibrium constant K.
Q3. According to Le Chatelier’s principle, if the pressure is increased on a system in equilibrium involving gases, the equilibrium shifts:
a) Towards side with more moles of gas
b) Towards side with fewer moles of gas
c) No shift
d) Randomly
Answer: b) Towards side with fewer moles of gas
Explanation: Increasing pressure favors the side with fewer gas molecules to reduce pressure.
More NEET Chemistry MCQs on Thermodynamics & Equilibrium
Q4. The change in internal energy of a system is zero in which of the following processes?
a) Adiabatic
b) Isothermal
c) Isobaric
d) Isochoric
Answer: b) Isothermal
Explanation: In an isothermal process, the temperature remains constant, so the internal energy change (ΔU) is zero.
Q5. Which law states that the total enthalpy change in a chemical reaction is the same, regardless of the number of steps in which the reaction occurs?
a) Hess’s Law
b) Dalton’s Law
c) Boyle’s Law
d) Avogadro’s Law
Answer: a) Hess’s Law
Explanation: Hess’s Law states that enthalpy change is path-independent and depends only on initial and final states.
Q6. At constant temperature and pressure, the criterion for spontaneity of a reaction is:
a) ΔH < 0
b) ΔS > 0
c) ΔG < 0
d) ΔU > 0
Answer: c) ΔG < 0
Explanation: The Gibbs free energy (ΔG) must be negative for a process to be spontaneous at constant temperature and pressure.
Q7. For the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), what happens to the equilibrium when the volume of the container is decreased?
a) Shifts to the right
b) Shifts to the left
c) No change
d) Reaction stops
Answer: a) Shifts to the right
Explanation: Decreasing volume increases pressure, shifting equilibrium towards the side with fewer gas molecules—in this case, the product side with 2 moles versus 4 moles on the reactant side.
Additional MCQs on Thermodynamics & Chemical Equilibrium for NEET
Q8. The entropy change of the universe for a spontaneous process is:
a) Zero
b) Positive
c) Negative
d) Depends on the system
Answer: b) Positive
Explanation: For a spontaneous process, the total entropy change of the universe (system + surroundings) always increases.
Q9. If ΔG for a reaction is zero, the system is:
a) At equilibrium
b) Spontaneous forward
c) Spontaneous backward
d) At standard state
Answer: a) At equilibrium
Explanation: When ΔG = 0, the reaction is at equilibrium and no net change occurs.
Q10. Which of the following is NOT affected by a catalyst in a reaction at equilibrium?
a) Activation energy
b) Equilibrium constant (K)
c) Reaction rate
d) Time to reach equilibrium
Answer: b) Equilibrium constant (K)
Explanation: Catalysts speed up the reaction but do not change the equilibrium position or the value of K.
Q11. The unit of the equilibrium constant Kp for the reaction:
2SO₂(g) + O₂(g) ⇌ 2SO₃(g) is:
a) atm⁻¹
b) atm
c) atm²
d) dimensionless
Answer: a) atm⁻¹
Explanation: For the reaction, Kp = (P_SO3)² / [(P_SO2)² * P_O2]. Units simplify to atm⁻¹.
More Practice MCQs for NEET Chemistry: Thermodynamics & Equilibrium
Q12. In an adiabatic expansion of an ideal gas, which of the following decreases?
a) Temperature
b) Pressure
c) Internal energy
d) All of the above
Answer: d) All of the above
Explanation: In an adiabatic expansion, no heat is exchanged (q = 0), the gas does work on surroundings, so temperature, pressure, and internal energy all decrease.
Q13. For a reaction at equilibrium, increasing the temperature will favor the endothermic direction if:
a) ΔH is positive
b) ΔH is negative
c) ΔS is zero
d) ΔG is zero
Answer: a) ΔH is positive
Explanation: Increasing temperature shifts equilibrium toward the endothermic side (positive ΔH) according to Le Chatelier’s principle.
Q14. Which thermodynamic function is used to determine the maximum useful work done by a system?
a) Enthalpy (H)
b) Entropy (S)
c) Gibbs free energy (G)
d) Internal energy (U)
Answer: c) Gibbs free energy (G)
Explanation: ΔG indicates the maximum non-expansion work obtainable from a reaction at constant temperature and pressure.
Q15. In a reaction mixture, if the concentration of products is increased, the equilibrium will:
a) Shift to products
b) Shift to reactants
c) Remain unchanged
d) Reaction stops
Answer: b) Shift to reactants
Explanation: According to Le Chatelier’s principle, adding more product shifts equilibrium backward to restore balance.
Additional NEET Chemistry MCQs: Thermodynamics & Equilibrium
Q16. The process in which ΔH is zero but ΔS is positive will be:
a) Always spontaneous
b) Always non-spontaneous
c) Spontaneous only at high temperature
d) Spontaneous only at low temperature
Answer: a) Always spontaneous
Explanation: When ΔH = 0 and ΔS > 0, ΔG = -TΔS which is always negative (spontaneous) at any temperature.
Q17. The equilibrium constant Kc for a reaction at 25°C is 1 × 10⁴. The reaction is:
a) Product-favored
b) Reactant-favored
c) At equilibrium, no change
d) Unpredictable
Answer: a) Product-favored
Explanation: A large Kc (>>1) means products are favored at equilibrium.
Q18. Which statement is true for the reaction quotient Q during the progress of a reaction?
a) Q = K at equilibrium
b) Q < K means forward reaction favored
c) Q > K means reverse reaction favored
d) All of the above
Answer: d) All of the above
Explanation: The relation between Q and K determines the direction of the reaction shift.
Q19. The standard entropy of a perfect crystal at absolute zero is:
a) Zero
b) Positive
c) Negative
d) Undefined
Answer: a) Zero
Explanation: According to the Third Law of Thermodynamics, the entropy of a perfect crystal at 0 K is zero.
Q20. Which of the following is NOT a thermodynamic state function?
a) Pressure
b) Volume
c) Work
d) Temperature
Answer: c) Work
Explanation: Work depends on the path taken, so it is not a state function.
Advanced NEET Chemistry MCQs: Thermodynamics & Equilibrium
Q21. Which of the following expressions correctly represents Gibbs free energy change (ΔG) at non-standard conditions?
a) ΔG = ΔG°
b) ΔG = ΔG° + RT ln Q
c) ΔG = -RT ln K
d) ΔG = ΔH - TΔS
Answer: b) ΔG = ΔG° + RT ln Q
Explanation: ΔG depends on the reaction quotient Q under non-standard conditions.
Q22. For an exothermic reaction, an increase in temperature will:
a) Increase equilibrium constant (K)
b) Decrease equilibrium constant (K)
c) Have no effect on K
d) Change K unpredictably
Answer: b) Decrease equilibrium constant (K)
Explanation: According to Le Chatelier’s principle, increasing temperature favors endothermic direction, decreasing K for exothermic reactions.
Q23. Which of the following is true for a spontaneous reaction?
a) ΔS_universe > 0
b) ΔG < 0
c) ΔH and ΔS may vary
d) All of the above
Answer: d) All of the above
Explanation: Spontaneous reactions increase the entropy of the universe and have negative Gibbs free energy.
Q24. At equilibrium, the partial pressure of gases in a reaction is:
a) Equal for all gases
b) Related by the equilibrium constant expression
c) Always the same as initial pressure
d) Zero
Answer: b) Related by the equilibrium constant expression
Explanation: Partial pressures satisfy the Kp expression at equilibrium.
Q25. The relation between Gibbs free energy and equilibrium constant K is:
a) ΔG° = -RT ln K
b) ΔG = -RT ln Q
c) ΔG = ΔH - TΔS
d) ΔG° = ΔH - TΔS
Answer: a) ΔG° = -RT ln K
Explanation: Standard Gibbs free energy change relates directly to the equilibrium constant.
Final Set of NEET Chemistry MCQs: Thermodynamics & Equilibrium
Q26. Which of the following processes is always spontaneous?
a) Melting of ice at 0°C
b) Freezing of water at 0°C
c) Expansion of gas into vacuum
d) Combustion of gasoline
Answer: c) Expansion of gas into vacuum
Explanation: Expansion into vacuum is spontaneous due to increase in entropy, without energy input.
Q27. When a system absorbs heat at constant pressure and temperature, the Gibbs free energy:
a) Increases
b) Decreases
c) Remains constant
d) May increase or decrease depending on reaction
Answer: d) May increase or decrease depending on reaction
Explanation: ΔG depends on ΔH and ΔS; heat absorption alone does not determine spontaneity.
Q28. Which of the following increases the entropy of the system?
a) Freezing of water
b) Dissolution of salt in water
c) Condensation of vapor
d) Crystallization
Answer: b) Dissolution of salt in water
Explanation: Dissolution increases disorder, thus increasing entropy.
Q29. For the reaction at equilibrium, if Q < K, the reaction will:
a) Shift forward to form more products
b) Shift backward to form more reactants
c) Remain at equilibrium
d) Stop
Answer: a) Shift forward to form more products
Explanation: If Q < K, the reaction shifts forward to reach equilibrium.
Q30. The entropy change (ΔS) for the reaction: N₂(g) + 3H₂(g) → 2NH₃(g) is:
a) Positive
b) Negative
c) Zero
d) Depends on temperature
Answer: b) Negative
Explanation: Number of gas molecules decreases, leading to decreased entropy.
Bonus MCQs for NEET Chemistry: Thermodynamics & Equilibrium
Q31. Which of the following statements about entropy is TRUE?
a) Entropy of a perfect crystal at 0 K is maximum
b) Entropy measures the disorder of a system
c) Entropy decreases in spontaneous processes
d) Entropy is a path function
Answer: b) Entropy measures the disorder of a system
Explanation: Entropy is a measure of randomness or disorder in the system.
Q32. The reaction N₂O₄(g) ⇌ 2NO₂(g) is endothermic. What happens when temperature is increased?
a) Equilibrium shifts to left
b) Equilibrium shifts to right
c) No change
d) Reaction stops
Answer: b) Equilibrium shifts to right
Explanation: Increasing temperature favors the endothermic direction.
Q33. Which quantity is zero at the critical point of a pure substance?
a) ΔH
b) ΔG
c) ΔS
d) ΔV
Answer: d) ΔV
Explanation: The volume change between liquid and vapor phases becomes zero at the critical point.
Q34. For an ideal gas, which process involves no change in internal energy?
a) Isothermal
b) Adiabatic
c) Isochoric
d) Isobaric
Answer: a) Isothermal
Explanation: Internal energy of an ideal gas depends only on temperature; no change in temperature means no change in internal energy.
Q35. Which of the following does NOT affect the equilibrium constant K?
a) Temperature
b) Pressure
c) Catalyst
d) Concentration
Answer: c) Catalyst
Explanation: Catalysts speed up both forward and backward reactions but do not change equilibrium constant.
Extra NEET Chemistry MCQs: Thermodynamics & Equilibrium
Q36. Which thermodynamic quantity is a measure of disorder or randomness in a system?
a) Enthalpy (H)
b) Entropy (S)
c) Gibbs free energy (G)
d) Internal energy (U)
Answer: b) Entropy (S)
Explanation: Entropy quantifies the degree of randomness or disorder in the system.
Q37. What is the sign of ΔH and ΔS for an exothermic reaction that is spontaneous at all temperatures?
a) ΔH negative, ΔS positive
b) ΔH positive, ΔS positive
c) ΔH negative, ΔS negative
d) ΔH positive, ΔS negative
Answer: a) ΔH negative, ΔS positive
Explanation: Both negative enthalpy and positive entropy changes favor spontaneity at all temperatures.
Q38. The equilibrium constant Kp for the reaction 2A(g) ⇌ B(g) + C(g) is 25 at a certain temperature. If initial pressure of A is 1 atm and no products are present, what direction will the reaction proceed?
a) Forward
b) Backward
c) No change
d) Cannot determine
Answer: a) Forward
Explanation: Initially Q = 0, less than Kp, so reaction shifts forward to form products.
Q39. Which of the following is NOT a criterion for spontaneity at constant temperature and pressure?
a) ΔG < 0
b) ΔH < 0 and ΔS > 0
c) ΔS_universe > 0
d) ΔU > 0
Answer: d) ΔU > 0
Explanation: Internal energy change alone does not determine spontaneity.
Q40. Which of the following reactions will have ΔS > 0?
a) Solid → liquid
b) Liquid → solid
c) Gas → liquid
d) Solid → gas
Answer: d) Solid → gas
Explanation: Transition from solid to gas significantly increases disorder.
Fresh NEET Chemistry MCQs: Thermodynamics & Equilibrium
Q41. The standard Gibbs free energy change (ΔG°) for a reaction is positive. This means the reaction is:
a) Spontaneous under standard conditions
b) Non-spontaneous under standard conditions
c) At equilibrium under standard conditions
d) Can’t be determined
Answer: b) Non-spontaneous under standard conditions
Explanation: Positive ΔG° means the reaction does not occur spontaneously at standard conditions.
Q42. Which of the following processes will lead to an increase in entropy (ΔS > 0)?
a) Condensation of water vapor
b) Freezing of liquid water
c) Vaporization of water
d) Crystallization of salt
Answer: c) Vaporization of water
Explanation: Vaporization increases disorder, hence increases entropy.
Q43. In a reaction where the equilibrium constant Kc = 1, which of the following is true?
a) Products are favored
b) Reactants are favored
c) Neither products nor reactants are favored; equilibrium lies midway
d) Reaction is irreversible
Answer: c) Neither products nor reactants are favored; equilibrium lies midway
Explanation: Kc = 1 means the concentrations of products and reactants are roughly equal at equilibrium.
Q44. Which of the following statements is FALSE?
a) Enthalpy is a state function
b) Work is a state function
c) Entropy is a state function
d) Internal energy is a state function
Answer: b) Work is a state function
Explanation: Work depends on the path and is not a state function.
Q45. In the reaction: 2NO₂(g) ⇌ N₂O₄(g), which of the following will shift the equilibrium towards the products?
a) Increasing temperature
b) Increasing pressure
c) Adding inert gas at constant volume
d) Decreasing pressure
Answer: b) Increasing pressure
Explanation: Increasing pressure favors the side with fewer moles of gas, here N₂O₄ (1 mole) over 2NO₂ (2 moles).
New NEET Chemistry MCQs: Thermodynamics & Equilibrium
Q46. What happens to the equilibrium constant K when a catalyst is added to a reaction?
a) Increases
b) Decreases
c) Remains the same
d) Depends on catalyst type
Answer: c) Remains the same
Explanation: A catalyst speeds up the rate of both forward and reverse reactions equally but does not change the equilibrium position or constant.
Q47. For the reaction , the equilibrium constant expression Kc is:
a)
b)
c)
d)
Answer: b)
Explanation: Kc is product concentrations over reactant concentrations, each raised to their stoichiometric coefficients.
Q48. Which of the following is TRUE about the sign of ΔS for the dissolution of salt in water?
a) Always positive
b) Always negative
c) Can be positive or negative
d) Zero
Answer: c) Can be positive or negative
Explanation: Entropy change depends on the nature of salt; some salts increase disorder, others may decrease it.
Q49. If ΔG for a reaction is zero, the reaction:
a) Is spontaneous
b) Is non-spontaneous
c) Is at equilibrium
d) Will not proceed
Answer: c) Is at equilibrium
Explanation: ΔG = 0 means the system is at equilibrium, no net change occurs.
Q50. Which of the following statements about the third law of thermodynamics is correct?
a) Entropy of a perfect crystal is zero at absolute zero
b) Entropy increases with temperature indefinitely
c) Enthalpy is zero at absolute zero
d) Internal energy is zero at absolute zero
Answer: a) Entropy of a perfect crystal is zero at absolute zero
Explanation: The third law states that the entropy of a perfect crystal at 0 K is zero.
More NEET Chemistry MCQs: Thermodynamics & Equilibrium
Q51. The entropy change of the universe for a spontaneous process is:
a) Positive
b) Negative
c) Zero
d) Depends on the process
Answer: a) Positive
Explanation: For any spontaneous process, the entropy of the universe increases.
Q52. Which of the following is a state function?
a) Heat
b) Work
c) Enthalpy
d) Path length
Answer: c) Enthalpy
Explanation: Enthalpy is a state function; heat and work are path functions.
Q53. The equilibrium constant Kc for a reaction is very small (<<1). This indicates:
a) Products are favored at equilibrium
b) Reactants are favored at equilibrium
c) Reaction is at equilibrium initially
d) Reaction is irreversible
Answer: b) Reactants are favored at equilibrium
Explanation: Small K means equilibrium lies towards reactants.
Q54. What is the effect of increasing pressure on the equilibrium of the reaction: ?
a) Shifts right
b) Shifts left
c) No effect
d) Reaction stops
Answer: a) Shifts right
Explanation: Increasing pressure favors the side with fewer gas moles (NH3 side).
Q55. At constant temperature and pressure, a reaction is spontaneous if:
a) ΔG > 0
b) ΔG = 0
c) ΔG < 0
d) ΔH > 0
Answer: c) ΔG < 0
Explanation: Negative Gibbs free energy indicates spontaneity.
NEET Chemistry MCQs: Thermodynamics & Equilibrium (Next Set)
Q56. Which law states that the entropy of a perfect crystal at absolute zero is zero?
a) First Law of Thermodynamics
b) Second Law of Thermodynamics
c) Third Law of Thermodynamics
d) Zeroth Law of Thermodynamics
Answer: c) Third Law of Thermodynamics
Explanation: The third law states entropy approaches zero as temperature approaches absolute zero.
Q57. In an exothermic reaction, increasing temperature will:
a) Increase equilibrium constant
b) Decrease equilibrium constant
c) No effect on equilibrium constant
d) Double the equilibrium constant
Answer: b) Decrease equilibrium constant
Explanation: Increasing temperature favors the endothermic direction, decreasing K for exothermic reactions.
Q58. The reaction quotient Q is calculated as:
a) Product concentrations/reactant concentrations at equilibrium
b) Product concentrations/reactant concentrations at any time
c) Only at standard conditions
d) None of the above
Answer: b) Product concentrations/reactant concentrations at any time
Explanation: Q can be calculated at any point during the reaction, not just at equilibrium.
Q59. Which of the following is NOT true about Gibbs free energy?
a) It predicts spontaneity of reactions
b) ΔG = 0 at equilibrium
c) It increases in spontaneous reactions
d) It depends on temperature
Answer: c) It increases in spontaneous reactions
Explanation: Gibbs free energy decreases in spontaneous reactions.
Q60. For the reaction , what happens to equilibrium if O₂ is removed?
a) Shifts right
b) Shifts left
c) No change
d) Reaction stops
Answer: b) Shifts left
Explanation: Removing a reactant shifts equilibrium to the left to replace it (Le Chatelier’s Principle).
NEET Chemistry MCQs: Thermodynamics & Equilibrium (New Set)
Q61. When a reaction reaches equilibrium, the rate of the forward reaction is:
a) Greater than the backward reaction
b) Less than the backward reaction
c) Equal to the backward reaction
d) Zero
Answer: c) Equal to the backward reaction
Explanation: At equilibrium, forward and reverse reaction rates are equal.
Q62. What happens to the Gibbs free energy change (ΔG) when a system reaches equilibrium?
a) ΔG > 0
b) ΔG < 0
c) ΔG = 0
d) ΔG becomes infinite
Answer: c) ΔG = 0
Explanation: At equilibrium, there is no net change, so ΔG is zero.
Q63. The equilibrium constant expression for the reaction is:
a)
b)
c)
d)
Answer: a)
Explanation: Products over reactants with their respective stoichiometric powers.
Q64. Which of the following will increase the value of the equilibrium constant for an exothermic reaction?
a) Increasing temperature
b) Decreasing temperature
c) Adding a catalyst
d) Increasing pressure
Answer: b) Decreasing temperature
Explanation: For exothermic reactions, lower temperatures favor product formation and increase K.
Q65. In thermodynamics, which term describes the maximum useful work obtainable from a process at constant temperature and pressure?
a) Enthalpy
b) Entropy
c) Gibbs free energy
d) Internal energy
Answer: c) Gibbs free energy
Explanation: Gibbs free energy indicates the maximum work that can be performed.
NEET Chemistry MCQs: Thermodynamics & Equilibrium (More Questions)
Q66. Which of the following is true for an endothermic reaction?
a) ΔH < 0
b) ΔH > 0
c) ΔS < 0
d) ΔG < 0 always
Answer: b) ΔH > 0
Explanation: Endothermic reactions absorb heat, so enthalpy change is positive.
Q67. If the reaction quotient Q equals the equilibrium constant K, what is the status of the reaction?
a) Reaction moves forward
b) Reaction moves backward
c) Reaction is at equilibrium
d) Reaction stops permanently
Answer: c) Reaction is at equilibrium
Explanation: When Q = K, the system is at equilibrium with no net change.
Q68. The entropy change of the surroundings is related to the enthalpy change of the system by:
a) ΔS_surroundings = -ΔH_system/T
b) ΔS_surroundings = ΔH_system/T
c) ΔS_surroundings = ΔG_system/T
d) ΔS_surroundings = 0
Answer: a) ΔS_surroundings = -ΔH_system/T
Explanation: The surroundings’ entropy change is related inversely to the system’s enthalpy change.
Q69. Which factor does NOT affect the value of equilibrium constant K?
a) Temperature
b) Pressure
c) Catalyst
d) Nature of reactants
Answer: c) Catalyst
Explanation: Catalyst speeds up attainment of equilibrium but does not change K.
Q70. For the reaction , if pressure is increased, the equilibrium will:
a) Shift to the right
b) Shift to the left
c) Remain unchanged
d) Reaction will stop
Answer: c) Remain unchanged
Explanation: Number of moles of gas is the same on both sides; pressure change has no effect.
NEET Chemistry MCQs: Thermodynamics & Equilibrium (New Questions)
Q71. Which quantity remains constant in an isothermal process?
a) Temperature
b) Pressure
c) Volume
d) Internal energy
Answer: a) Temperature
Explanation: Isothermal means constant temperature throughout the process.
Q72. The reaction is exothermic. If temperature is increased, the equilibrium constant K will:
a) Increase
b) Decrease
c) Remain unchanged
d) Become zero
Answer: b) Decrease
Explanation: For exothermic reactions, increasing temperature shifts equilibrium towards reactants, lowering K.
Q73. The second law of thermodynamics states that:
a) Energy can neither be created nor destroyed
b) Entropy of the universe always decreases
c) Entropy of the universe always increases
d) The total energy of a system is constant
Answer: c) Entropy of the universe always increases
Explanation: This law indicates spontaneous processes increase universal entropy.
Q74. What is the unit of the equilibrium constant Kc for the reaction ?
a) mol/L
b) mol/L²
c) mol⁻¹L
d) Unitless
Answer: c) mol⁻¹L
Explanation: Kc units depend on stoichiometry; here, products/reactants give mol⁻¹L.
Q75. In which of the following cases is ΔS positive?
a) Water freezing to ice
b) Melting of ice
c) Condensation of steam
d) Deposition of frost
Answer: b) Melting of ice
Explanation: Melting increases disorder, so entropy increases.
NEET Chemistry MCQs: Thermodynamics & Equilibrium (New Set)
Q76. Which of the following is NOT a characteristic of an adiabatic process?
a) No heat exchange with surroundings
b) ΔQ = 0
c) Temperature remains constant
d) Work done changes internal energy
Answer: c) Temperature remains constant
Explanation: In adiabatic processes, temperature usually changes because no heat is exchanged.
Q77. The equilibrium constant K for the reaction is 10 at 25°C. If the concentration of A is 0.5 M and B is 2 M, what is the reaction quotient Q? Will the reaction proceed forward or backward?
a) Q = 4, proceed backward
b) Q = 4, proceed forward
c) Q = 0.25, proceed forward
d) Q = 0.25, proceed backward
Answer: a) Q = 4, proceed backward
Explanation: Q = [B]/[A] = 2/0.5 = 4; since Q > K, reaction shifts backward.
Q78. What is the effect of adding an inert gas at constant volume on the position of equilibrium?
a) Shifts right
b) Shifts left
c) No effect
d) Equilibrium constant changes
Answer: c) No effect
Explanation: Adding inert gas at constant volume does not change partial pressures; equilibrium remains unchanged.
Q79. Which thermodynamic function is maximum at equilibrium for a system at constant temperature and pressure?
a) Enthalpy
b) Entropy
c) Gibbs free energy
d) Helmholtz free energy
Answer: b) Entropy
Explanation: Entropy is maximized at equilibrium for an isolated system.
Q80. For a reaction where ΔH is positive and ΔS is positive, the reaction is spontaneous at:
a) Low temperature only
b) High temperature only
c) All temperatures
d) No temperature
Answer: b) High temperature only
Explanation: At high T, the TΔS term dominates making ΔG negative.
NEET Chemistry MCQs: Thermodynamics & Equilibrium (Fresh Questions)
Q81. Which of the following will NOT affect the value of the equilibrium constant K?
a) Temperature
b) Pressure
c) Catalyst
d) Concentration of reactants
Answer: c) Catalyst
Explanation: Catalyst speeds up the rate but does not change the equilibrium position or K.
Q82. In an exothermic reaction, if temperature is increased, the equilibrium constant K:
a) Increases
b) Decreases
c) Remains unchanged
d) Becomes zero
Answer: b) Decreases
Explanation: Increasing temperature favors endothermic direction, decreasing K for exothermic reactions.
Q83. For the reaction , if pressure is increased, the equilibrium will:
a) Shift to the right
b) Shift to the left
c) Remain unchanged
d) Stop
Answer: a) Shift to the right
Explanation: Increase in pressure favors the side with fewer moles of gas.
Q84. Entropy (S) is:
a) A measure of disorder
b) A state function
c) Increased in spontaneous processes
d) All of the above
Answer: d) All of the above
Explanation: Entropy measures disorder, is a state function, and tends to increase in spontaneous processes.
Q85. What is the sign of ΔG for a non-spontaneous reaction?
a) Positive
b) Negative
c) Zero
d) Undefined
Answer: a) Positive
Explanation: Positive ΔG indicates non-spontaneity under given conditions.
NEET Chemistry MCQs: Thermodynamics & Equilibrium (Latest Set)
Q86. Which of the following processes has a negative ΔS?
a) Melting of ice
b) Vaporization of water
c) Condensation of steam
d) Sublimation of dry ice
Answer: c) Condensation of steam
Explanation: Condensation changes gas to liquid, decreasing disorder, so ΔS is negative.
Q87. At equilibrium, the value of Gibbs free energy change ΔG is:
a) Positive
b) Negative
c) Zero
d) Undefined
Answer: c) Zero
Explanation: At equilibrium, no net change occurs, so ΔG = 0.
Q88. If a reaction is endothermic and spontaneous at high temperature, what can be said about ΔH and ΔS?
a) ΔH > 0, ΔS < 0
b) ΔH < 0, ΔS > 0
c) ΔH > 0, ΔS > 0
d) ΔH < 0, ΔS < 0
Answer: c) ΔH > 0, ΔS > 0
Explanation: Positive ΔS and ΔH mean spontaneity at high T where TΔS outweighs ΔH.
Q89. Which law relates the change in entropy of the universe to spontaneity of a process?
a) First law of thermodynamics
b) Second law of thermodynamics
c) Third law of thermodynamics
d) Hess’s law
Answer: b) Second law of thermodynamics
Explanation: It states that the entropy of the universe always increases for spontaneous processes.
Q90. In the reaction , increasing the concentration of HI will:
a) Shift equilibrium right
b) Shift equilibrium left
c) Increase equilibrium constant
d) Decrease equilibrium constant
Answer: b) Shift equilibrium left
Explanation: According to Le Chatelier’s principle, increasing product shifts equilibrium towards reactants.
NEET Chemistry MCQs: Thermodynamics & Equilibrium (Fresh Batch)
Q91. Which quantity is a measure of randomness or disorder in a system?
a) Enthalpy
b) Entropy
c) Gibbs free energy
d) Internal energy
Answer: b) Entropy
Explanation: Entropy (S) quantifies the degree of disorder or randomness in a system.
Q92. What happens to the equilibrium constant K when temperature is increased for an endothermic reaction?
a) K increases
b) K decreases
c) K remains the same
d) K becomes zero
Answer: a) K increases
Explanation: Increasing temperature favors endothermic reactions, increasing K.
Q93. For the reaction , if Q > K, the reaction will:
a) Proceed forward
b) Proceed backward
c) Remain at equilibrium
d) Stop
Answer: b) Proceed backward
Explanation: When Q > K, the reaction shifts toward reactants to reestablish equilibrium.
Q94. The value of ΔG° for a spontaneous reaction under standard conditions is:
a) Positive
b) Negative
c) Zero
d) Infinite
Answer: b) Negative
Explanation: Negative standard Gibbs free energy change indicates spontaneity.
Q95. Which of the following is true for a reaction with ΔH = 0 and ΔS > 0?
a) Spontaneous at all temperatures
b) Non-spontaneous at all temperatures
c) Spontaneous only at low temperatures
d) Spontaneous only at high temperatures
Answer: a) Spontaneous at all temperatures
Explanation: With ΔH = 0 and positive ΔS, ΔG = -TΔS < 0 always, so spontaneous at all T.
NEET Chemistry MCQs: Thermodynamics & Equilibrium (New Questions)
Q96. The internal energy of an ideal gas depends on:
a) Pressure
b) Volume
c) Temperature
d) Number of moles only
Answer: c) Temperature
Explanation: For ideal gases, internal energy depends only on temperature.
Q97. The sign of ΔG for a reaction at equilibrium is:
a) Positive
b) Negative
c) Zero
d) Depends on temperature
Answer: c) Zero
Explanation: At equilibrium, Gibbs free energy change is zero.
Q98. Which law states that the entropy of a perfect crystal at absolute zero is zero?
a) First law of thermodynamics
b) Second law of thermodynamics
c) Third law of thermodynamics
d) Hess’s law
Answer: c) Third law of thermodynamics
Explanation: The third law states entropy at absolute zero is zero for a perfect crystal.
Q99. For the reaction , if volume is decreased, equilibrium will:
a) Shift right
b) Shift left
c) Remain unchanged
d) Shift randomly
Answer: a) Shift right
Explanation: Decreasing volume favors side with fewer moles of gas, which is the right side.
Q100. In a spontaneous process at constant temperature and pressure, the Gibbs free energy:
a) Increases
b) Decreases
c) Remains constant
d) Can increase or decrease
Answer: b) Decreases
Explanation: Spontaneous processes decrease Gibbs free energy under constant T and P.
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