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Equilibrium appeared 35 times across 3 years — 4.1% of Chemistry. This question is from Le Chatelier's Principle.

Year 2026 2025 2024 Total
Questions 10 17 8 35

Consider the equilibrium CO(g) + 3H₂(g) leftharpoons CH₄(g) + H₂O(g) If the pressure applied over the system increases by two fold at constant temperature then: (A) Concentration of reactants and products increases. (B) Equilibrium will shift in forward direction. (C) Equilibrium constant increases since concentration of products increases. (D) Equilibrium constant remains unchanged as concentration of reactants and products remain same. Choose the correct answer from the options given below:

Solution & Explanation

Core Logic

Statement (A) is correct: Increasing pressure by compressing the volume increases active mass/concentration (c = n/V) for both reactants and products instantly. Statement (B) is correct: The reaction has Delta ng = 2 - 4 = -2. Increasing pressure shifts equilibrium towards the direction of fewer gaseous moles, which is the forward path. Statement (C) is incorrect: Equilibrium constant (K) is exclusively temperature-dependent and does not alter with pressure changes. Statement (D) is correct: Confirms that equilibrium constant remains unchanged.

Pattern Recognition

Always remember: pressure changes shift positions but NEVER alter the value of the equilibrium constant Kc or Kₚ. Only temperature changes can change K.

Chapter Mix

Class 11 Chemistry: Equilibrium

Reference Study Guides

More Equilibrium Previous-Year Questions — Page 7

Q84 jee_main_2024_29_jan_morning Kp and Kc Relationship
For the reaction N₂O₄(g) leftharpoons 2NO₂(g) Kₚ = 0.492 atm at 300K . Kc for the reaction at same temperature is ______ × 10⁻² . (Given: R = 0.082 L atm mol⁻¹ K⁻¹)
Numerical Answer. Answer: 2 to 2

Solution

Related Formula
Kₚ = Kc · (RT)Δ ng
Core Logic

For the given gaseous equilibrium reaction:

N₂O₄(g) leftharpoons 2NO₂(g)

First, find the change in the number of moles of gas (Δ ng):

Δ ng = nₚ - nᵣ = 2 - 1 = 1
Step 1: Calculation

Substitute the given values into the Kₚ - Kc relationship: Kₚ = 0.492 R = 0.082 T = 300 K

0.492 = Kc · (0.082 × 300)¹ Kc = (0.492)/(0.082 × 300) Kc = (0.492)/(24.6)

Kc = 0.02

Converting to the requested format (x × 10⁻²):

Kc = 2 × 10⁻²

So, the value is 2.

Chapter Mix

Class 11 Chemistry: Equilibrium

Q85 jee_main_2024_30_january_evening Buffer Solutions
The pH of an aqueous solution containing 1M benzoic acid (pKₐ = 4.20) and 1M sodium benzoate is 4.5. The volume of benzoic acid solution in 300 mL of this buffer solution is ______ mL.
Numerical Answer. Answer: 100 to 100

Solution

Related Formula

Henderson-Hasselbalch Equation for Acidic Buffers:

pH = pKₐ + ( [Salt][Acid] )
Core Logic

Let the volume of 1M Benzoic acid be Vₐ mL and the volume of 1M Sodium benzoate be Vₛ mL. Total volume = Vₛ + Vₐ = 300 mL.

Millimoles of acid = 1 × Vₐ = Vₐ Millimoles of salt = 1 × Vₛ = Vₛ

Applying Henderson's Equation:

4.5 = 4.2 + ((Vₛ)/(Vₐ))
Step 1: Calculate Volume Ratio
((Vₛ)/(Vₐ)) = 4.5 - 4.2 = 0.3

Since 2 ≈ 0.3, we have:

(Vₛ)/(Vₐ) = 2

Vₛ = 2 Vₐ

Step 2: Substitute and Solve

We know Vₛ + Vₐ = 300 Substituting Vₛ = 2 Vₐ:

2 Vₐ + Vₐ = 300

3 Vₐ = 300

Vₐ = 100 mL
Chapter Mix

Class 11 Chemistry: Equilibrium

Q82 jee_main_2024_30_jan_morning Solubility Product
The pH at which Mg(OH)₂ [Kₛₚ=1× 10⁻¹¹] begins to precipitate from a solution containing 0.10 M Mg²⁺ ions is
Numerical Answer. Answer: 9 to 9

Solution

Related Formula
Kₛₚ = [Mg²⁺][OH^-]² pOH = - [OH^-]

pH + pOH = 14

Core Logic

Precipitation begins just when the ionic product equals the solubility product (Qₛₚ = Kₛₚ).

Step 1: Calculating required [OH-]
[Mg²⁺][OH^-]² = 10⁻¹¹

Given [Mg²⁺] = 0.10 M

0.10 × [OH^-]² = 10⁻¹¹ [OH^-]² = 10⁻¹⁰ [OH^-] = 10⁻⁵ M
Step 2: Finding pH
pOH = - (10⁻⁵) = 5

pH = 14 - pOH pH = 14 - 5 = 9

Chapter Mix

Class 11 Chemistry: Equilibrium

Q71 jee_main_2024_31_jan_evening Equilibrium Constants (Kp and Kc)
A(g) leftharpoons B(g) + (C)/(2)(g) The correct relationship between KP, α and equilibrium pressure P is
  • A. KP = α(1)/(2)P(1)/(2)(2 + α)(1)/(2)
  • B. KP = α(3)/(2)P(1)/(2)(2 + α)(1)/(2)(1 - α)
  • C. KP = α(1)/(2)P(3)/(2)(2 + α)(3)/(2)
  • D. KP = α(1)/(2)P(1)/(2)(2 + α)(3)/(2)

Solution

Related Formula
KP = PB · (PC)(1)/(2)PA

where Pᵢ is the partial pressure of component i.

Step 1: Setting up the ICE Table

For the reaction A(g) leftharpoons B(g) + (1)/(2) C(g)

Let initial moles of A = 1. At equilibrium: Moles of A = 1 - α Moles of B = α Moles of C = (α)/(2)

Total moles at equilibrium = (1 - α) + α + (α)/(2) = 1 + (α)/(2) = (2 + α)/(2)

Step 2: Calculating Partial Pressures

Using mole fraction × Total Pressure (P): PA = (1 - α)/(1 + (α)/(2)) · P PB = (α)/(1 + (α)/(2)) · P PC = ((α)/(2))/(1 + (α)/(2)) · P

Step 3: Calculating Kp
KP = PB · (PC)(1)/(2)PA KP = ( (α)/(1 + α/2) P ) · ( (α/2)/(1 + α/2) P )1/2(1 - α)/(1 + α/2) P KP = α · (α/2)1/2 · P3/2(1 + α/2)3/2 · (1 + α/2)/((1 - α) P) KP = α3/2 · P1/2√(2) · (1 + α/2)1/2 · (1 - α)

Since 1 + α/2 = (2+α)/(2), the √(2) in denominator cancels out perfectly leaving:

KP = α(3)/(2) P(1)/(2)(2 + α)(1)/(2)(1 - α)
Chapter Mix

Class 11 Chemistry: Equilibrium

Q62 jee_main_2024_31_jan_morning Equilibrium Constant
For the given reaction, choose the correct expression of KC from the following :- Fe(aq)³⁺ + SCN(aq)⁻ leftharpoons (FeSCN)(aq)²⁺
  • A. KC = [FeSCN²⁺][Fe³⁺][SCN⁻]
  • B. KC = [Fe³⁺][SCN⁻][FeSCN²⁺]
  • C. KC = [FeSCN²⁺][Fe³⁺]²[SCN⁻]²
  • D. KC = [FeSCN²⁺]²[Fe³⁺][SCN⁻]

Solution

Related Formula
KC = [Products][Reactants]
Core Logic
KC = Products ion conc.Reactants ion conc. KC = [FeSCN²⁺][Fe³⁺][SCN⁻]
Chapter Mix

Class 11 Chemistry: Equilibrium

More Equilibrium Questions — jee_main_2025_29_jan_evening

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