What does Equilibrium cover for NEET Chemistry?

9 lessons: Acid Base Concepts, Buffer Solutions, Common Ion Effect, Dynamic Equilibrium, Law of Equilibrium Kp Kc, Le Chatelier, pH Scale, Solubility Product and Weak Strong Electrolytes.

How often has Equilibrium come up in NEET past papers?

Our set of verified past papers has 15 questions from this unit, from NEET 2020, 2021, 2022, 2023, 2024, 2025 and 2026. Each is answered against the official NTA key.

Is the Equilibrium material free?

Yes. All 9 lessons and 72 practice questions are free, with no login needed.

Equilibrium

9 lessons

Topic index in NCERT order

9 of 9 lessons by the NCERT chapter they teach from, in book order. The page is the first printed page of your NCERT book the lesson cites; PYQs are the past NEET questions on that topic.

Class 11 Chemistry, Chapter 6

Dynamic Equilibriump. 1680 PYQs
Law of Equilibrium Kp Kcp. 1755 PYQs
Le Chatelierp. 1851 PYQ
Acid Base Conceptsp. 1901 PYQ
pH Scalep. 1911 PYQ
Weak Strong Electrolytesp. 1980 PYQs
Common Ion Effectp. 2012 PYQs
Buffer Solutionsp. 2031 PYQ
Solubility Productp. 2051 PYQ

Acid Base Concepts

8 MCQs1 PYQsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (2)

Buffer Solutions

8 MCQs1 PYQs3 revision cardsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (1)Calculation (1)

Common Ion Effect

8 MCQs2 PYQs3 revision cardsWorked example

Direct Application (3)Easy Recall (3)Calculation (2)

Dynamic Equilibrium

8 MCQsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (2)

Law of Equilibrium Kp Kc

8 MCQs5 PYQs3 revision cardsWorked example

Direct Application (3)Calculation (2)Easy Recall (2)Concept Trap (1)

Le Chatelier

8 MCQs1 PYQsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (2)

pH Scale

8 MCQs1 PYQs3 revision cardsWorked example

Easy Recall (3)Direct Application (3)Calculation (1)Concept Trap (1)

Solubility Product

8 MCQs1 PYQs3 revision cardsWorked example

Easy Recall (3)Direct Application (3)Calculation (2)

Weak Strong Electrolytes

8 MCQs3 revision cardsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (1)Calculation (1)

Past-paper questions from this unit

15 questions from NEET 2020, 2021, 2022, 2023, 2024, 2025, 2026. Answers verified against NTA official keys.

By year in our set: 2020 (2) · 2021 (1) · 2022 (2) · 2023 (2) · 2024 (4) · 2025 (3) · 2026 (1)

Lesson: Solubility Product

NEET 2026

The correct order of solubility of the given salts in water at 298 K is, given K_sp at 298 K : AgBr 5.0×10⁻¹³, Zn(OH)₂ 1.0×10⁻¹⁵, Hg₂Cl₂ 1.3×10⁻¹⁸ :

1Hg₂Cl₂ > Zn(OH)₂ > AgBr

2AgBr > Zn(OH)₂ > Hg₂Cl₂

3Hg₂Cl₂ > AgBr > Zn(OH)₂

4Zn(OH)₂ > AgBr > Hg₂Cl₂

NTA Answer: Option 4(final)

Report an error · Every fix is public: corrections log

Lesson: pH Scale

NEET 2025

Phosphoric acid ionizes in three steps with their ionization constant values Kₐ₁, Kₐ₂ and Kₐ₃, respectively, while K is the overall ionization constant. Which of the following statements are true? A. log K = log Kₐ₁ + log Kₐ₂ + log Kₐ₃ B. H₃PO₄ is a stronger acid than H₂PO₄⁻ and HPO₄²⁻ C. Kₐ₁ > Kₐ₂ > Kₐ₃ D. Kₐ₁ = (Kₐ₃ + Kₐ₂)/2 Choose the correct answer from the options given below :

1A, B and C only

2A and B only

3A and C only

4B, C and D only

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Lesson: Le Chatelier

NEET 2025

Higher yield of NO in N₂(g) + O₂(g) ⇌ 2NO(g) can be obtained at [ΔH of the reaction = +180.7 kJ mol⁻¹] A. Higher temperature B. Lower temperature C. Higher concentration of N₂ D. Higher concentration of O₂ Choose the correct answer from the options given below :

1A, C, D only

2A, D only

3B, C only

4B, C, D only

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Lesson: Law of Equilibrium Kp Kc

NEET 2025

For the reaction A(g) ⇌ 2B(g), the backward reaction rate constant is higher than the forward reaction rate constant by a factor of 2500, at 1000 K. [Given : R = 0.0831 L atm mol⁻¹ K⁻¹] K_P for the reaction at 1000 K is

10.021

283.1

32.077 × 10⁵

40.033

NTA Answer: Option 4(final)

Report an error · Every fix is public: corrections log

NEET 2024Revised key

The Henry’s law constant (K ) values of three gases (A, B, C) in water are 145, 2 × 10⁻⁵ and 35 kbar, H respectively. The solubility of these gases in water follow the order:

1B > A > C

2B > C > A

3A > C > B

4A > B > C

NTA Answer: Option 2(revised_final)

Report an error · Every fix is public: corrections log

Lesson: Law of Equilibrium Kp Kc

NEET 2024Revised key

In which of the following equilibria, K_p and K_c are NOT equal?

1PCl₅(g) ⇌ PCl₃(g) + Cl₂(g)

2H₂(g) + I₂(g) ⇌ 2HI(g)

3CO(g) + H₂O(g) ⇌ CO₂(g) + H₂(g)

42BrCl(g) ⇌ Br₂(g) + Cl₂(g)

NTA Answer: Option 1(revised_final)

Report an error · Every fix is public: corrections log

Lesson: Law of Equilibrium Kp Kc

NEET 2024Revised key

C [A] = [B] = [C] = 2 × 10⁻³ M. Then, which of the following is correct?

1Reaction is at equilibrium.

2Reaction has a tendency to go in forward direction.

3Reaction has a tendency to go in backward direction.

4Reaction has gone to completion in forward direction.

NTA Answer: Option 3(revised_final)

Report an error · Every fix is public: corrections log

Lesson: Law of Equilibrium Kp Kc

NEET 2024Revised key

Consider the following reaction in a sealed vessel at equilibrium with concentrations of N₂ = 3.0 × 10⁻³ M, O₂ = 4.2 × 10⁻³ M and NO = 2.8 × 10⁻³ M. 2NO(g) ⇌ N₂(g) + O₂(g) If 0.1 mol L⁻¹ of NO(g) is taken in a closed vessel, what will be degree of dissociation (α) of NO(g) at equilibrium?

10.00889

20.0889

30.8889

40.717

NTA Answer: Option 4(revised_final)

Report an error · Every fix is public: corrections log

NEET 2023

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R Assertion A : Helium is used to dilute oxygen in diving apparatus. Reason R : Helium has high solubility in O . 2 In the light of the above statements, choose the correct answer from the options given below

1Both A and R are true and R is NOT the correct explanation of A

2A is true but R is false

3A is false but R is true

4Both A and R are true and R is the correct explanation of A

NTA Answer: Option 2(final)

Report an error · Every fix is public: corrections log

Lesson: Acid Base Concepts

NEET 2023

Amongst the given options which of the following molecules/ ion acts as a Lewis acid?

1H₂O

2BF₃

3OH⁻

4NH₃

NTA Answer: Option 2(final)

Report an error · Every fix is public: corrections log

Lesson: Buffer Solutions

NEET 2022

The pH of the solution containing 50 mL each of 0.10 M sodium acetate and 0.01 M acetic acid is [Given pKa of CH3COOH = 4.57]

12.57

25.57

33.57

44.57

NTA Answer: Option 2(final)

Report an error · Every fix is public: corrections log

Lesson: Law of Equilibrium Kp Kc

NEET 2022

3O₂(g) ⇌ 2O₃(g) For the above reaction at 298 K, K_C is found to be 3.0 × 10⁻⁵⁹. If the concentration of O₂ at equilibrium is 0.040 M then concentration of O₃ in M is

11.2 × 10²¹

24.38 × 10⁻³²

31.9 × 10⁻⁶³

42.4 × 10³¹

NTA Answer: Option 2(final)

Report an error · Every fix is public: corrections log

NEET 2021

The pK of dimethylamine and pK of acetic acid are b a 3.27 and 4.77 respectively at T (K). The correct option for the pH of dimethylammonium acetate solution is :

16.25

28.50

35.50

47.75

NTA Answer: Option 4(final)

Report an error · Every fix is public: corrections log

Lesson: Common Ion Effect

NEET 2020

Find out the solubility of Ni(OH)2 in 0.1 M NaOH. Given that the ionic product of Ni(OH)2 is 2×10⁻¹⁵.

11×10⁸ M

22×10⁻¹³ M

32×10⁻⁸ M

41×10⁻¹³ M

NTA Answer: Option 2(final)

Report an error · Every fix is public: corrections log

Lesson: Common Ion Effect

NEET 2020

HCl was passed through a solution of CaCl2 , MgCl2 and NaCl. Which of the following compound(s) crystallise(s) ?

1NaCl, MgCl2 and CaCl2

2Both MgCl2 and CaCl2

3Only NaCl

4Only MgCl2

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

Exam traps and common mistakes in this unit

Lesson: Law of Equilibrium Kp Kc

Trap

Δn sign in K_p ↔ K_c conversion

Category: Sign Convention

Δn = (mol gas product) - (mol gas reactant). Sign matters; K_p = K_c (RT)^Δn.

When it triggers

Convert K_p ↔ K_c for gas-phase reaction.

How to avoid

Count moles of gas only (ignore solids/liquids). Δn = product - reactant. If Δn = 0, K_p = K_c. If Δn = +1, K_p = K_c × RT.

Lesson: Le Chatelier

Trap

Catalyst does NOT shift equilibrium

Category: Overthinking

Student claims catalyst shifts equilibrium toward products. Catalyst speeds up forward AND reverse equally; equilibrium position unchanged.

When it triggers

Question lists catalyst addition among options for shifting equilibrium.

How to avoid

Catalyst lowers activation energy of BOTH forward and reverse reactions equally. Time to reach equilibrium decreases; equilibrium position is unchanged.

Lesson: Solubility Product

Trap

K_sp stoichiometric powers

Category: Similar Terms

For salt M_aX_b: K_sp = [M⁺]^a [X⁻]^b. Student uses [M⁺][X⁻] regardless of stoichiometry.

When it triggers

K_sp problem with non-1:1 salt (e.g. CaF₂, Mg(OH)₂, Ag₂CrO₄).

How to avoid

Write dissolution: M_aX_b → aM + bX. Then K_sp = [M]^a · [X]^b. For CaF₂ ↔ Ca + 2F: K_sp = s · (2s)² = 4s³.

Lesson: Law of Equilibrium Kp Kc

Mistake

Counts solid/liquid moles in Δn for K_p ↔ K_c conversion.

Root cause: concept gap

Correction

Δn = (moles GAS product) - (moles GAS reactant). Solids and liquids excluded.

Lesson: Le Chatelier

Mistake

Believes catalyst shifts equilibrium toward products.

Root cause: concept gap

Correction

Catalyst speeds up forward AND reverse equally. Equilibrium position is unchanged. Time to reach equilibrium decreases.

Lesson: Le Chatelier

Mistake

Predicts wrong direction of shift on pressure change.

Root cause: concept gap

Correction

Increase P → shift toward FEWER moles of gas. Decrease P → shift toward MORE moles. Reactions with same number of moles of gas: P doesn't shift equilibrium.

Lesson: pH Scale

Mistake

Treats weak acid as fully dissociated when computing pH.

Root cause: concept gap

Correction

Weak acid: only fraction ionises. [H+] ≈ √(Ka · C). For 0.1 M acetic acid (Ka ~10⁻⁵): [H+] ~10⁻³ (pH ~3), not 1 (pH=1).

Lesson: Solubility Product

Mistake

Uses K_sp = [M+][X-] regardless of salt stoichiometry.

Root cause: formula misuse

Correction

For M_aX_b: K_sp = [M]^a · [X]^b. CaF₂: K_sp = s · (2s)² = 4s³.

Formulas in this unit

Lesson: Buffer Solutions

Henderson-Hasselbalch (buffer)

pH = p K_{a} + lo g \frac{[ salt ]}{[ acid ]}

pH of acidic buffer in terms of conjugate base/acid concentrations. For basic buffer: pOH = pKb + log10([salt]/[base]).

Symbol	Quantity	SI Unit
pKa	-log Ka	-
[salt]	conjugate base conc	mol/L
[acid]	weak acid conc	mol/L

Valid when

Buffer (weak acid + conjugate base)
Concentrations not too dilute
Approximate (assumes negligible dissociation)

Lesson: Law of Equilibrium Kp Kc

Equilibrium constant K_p and K_c

K_{p} = K_{c} (R T)^{Δ n}

Convert between pressure-based and concentration-based equilibrium constants. T in K; R = 0.0821 L atm/mol/K (when K_p in atm).

Symbol	Quantity	SI Unit
K_p	pressure constant	-
K_c	concentration constant	-
Δn	mole change	-

Valid when

Gas-phase equilibrium
Same temperature

Lesson: pH Scale

pH and pOH

pH = - lo g [H^{+}]

Logarithmic acidity scale. Pure water at 25°C: pH = 7 = pOH.

Symbol	Quantity	SI Unit
[H+]	hydrogen ion conc	mol/L
[OH-]	hydroxide conc	mol/L

Valid when

Aqueous solution
Use Kw = 10^-14 at 25°C

Lesson: Solubility Product

Solubility product

K_{sp} = [M^{+}]^{a} [X^{-}]^{b}

Equilibrium constant for sparingly soluble salt. Q < K_sp: dissolves; Q > K_sp: precipitates.

Symbol	Quantity	SI Unit
K_sp	solubility product	-

Valid when

Sparingly soluble salt
Saturated solution

Lesson: Weak Strong Electrolytes

Ka, Kb, Kw relationship

K_{a} K_{b} = K_{w}

Stronger acid → weaker conjugate base, and vice versa. pKa + pKb = 14.

Symbol	Quantity	SI Unit
Ka	acid dissociation	-
Kb	base dissociation	-
Kw	water 10^-14	-

Valid when

Conjugate acid-base pair
25°C

NEET question patterns in this unit

Lesson: Law of Equilibrium Kp Kc

Convert between K_p and K_c using K_p = K_c (RT)^Δn. Identify Δn carefully.

Multi StepMedium

Common distractors

wrong delta n sign

Counts moles incorrectly

Lesson: Le Chatelier

Predict equilibrium shift on changing concentration, P, T, or adding catalyst.

InterpretationMedium

Common distractors

treats catalyst as shifting

Believes catalyst shifts equilibrium

Lesson: pH Scale

Compute pH of weak acid/base solution using Ka or Kb. Approximation: [H+] ≈ √(Ka·C).

Multi StepMedium

Common distractors

ignores weak vs strong

Treats weak acid as fully dissociated

Lesson: Solubility Product

Compute solubility from K_sp or vice versa. Apply common-ion effect when relevant.

Multi StepMedium

Common distractors

forgets stoichiometric coefficient power

Uses [M+]^1 [X-]^1 for M(X)_2 salt

Questions about this unit

What does Equilibrium cover for NEET Chemistry?: 9 lessons: Acid Base Concepts, Buffer Solutions, Common Ion Effect, Dynamic Equilibrium, Law of Equilibrium Kp Kc, Le Chatelier, pH Scale, Solubility Product and Weak Strong Electrolytes.
How often has Equilibrium come up in NEET past papers?: Our set of verified past papers has 15 questions from this unit, from NEET 2020, 2021, 2022, 2023, 2024, 2025 and 2026. Each is answered against the official NTA key.
Is the Equilibrium material free?: Yes. All 9 lessons and 72 practice questions are free, with no login needed.