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Equilibrium appeared 36 times across 3 years — 4.2% of Chemistry. This question is from pH of Weak Acids.

Year 2026 2025 2024 Total
Questions 10 18 8 36
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Consider the dissociation equilibrium of the following weak acid HA leftharpoons H⁺(aq) + A⁻(aq) If the pKₐ of the acid is 4, then the pH of 10~mM HA solution is _____. (Nearest integer) [Given : The degree of dissociation can be neglected with respect to unity]

Numerical Answer Type:
Enter a numerical value Answer: 3 to 3 +4 marks

Solution & Explanation

Related Formula
pH = (1)/(2) [pKₐ - C]
Step 1: Identify Parameters

pKₐ = 4

Concentration C = 10~mM = 10 × 10⁻³~M = 10⁻²~M

Step 2: Execute Calculation
pH = (1)/(2) [4 - (10⁻²)] = (1)/(2) [4 - (-2)] = (1)/(2) [6] = 3
Pattern Recognition

For weak monoprotic acids where α ll 1, the pH is always the arithmetic mean of the pKₐ and the negative logarithm of molarity.

Chapter Mix

Class 11 Chemistry: Equilibrium

Acid dissociation visualization
Acid dissociation visualization

Reference Study Guides

Equilibrium

More Equilibrium Previous-Year Questions — Page 8

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_2026_28_january_morning

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Rankbit System
JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)