Acids and Bases — Arrhenius, Brønsted-Lowry, Lewis
Ionic Equilibrium
6
JEE Qs
8%
Hard
60
min
Master the definitions, identify examples, and understand the hierarchy and interrelationships between Arrhenius, Brønsted-Lowry, and Lewis theories to tackle conceptual questions effectively.
🧮 Key Formulas
✅ Key Points for JEE
- 1Arrhenius theory is limited to aqueous solutions and species producing H⁺ or OH⁻ ions.
- 2Brønsted-Lowry theory expands definition to proton (H⁺) transfer, applicable to non-aqueous solutions, and introduces conjugate acid-base pairs.
- 3A species acting as a Brønsted-Lowry acid loses a proton to form its conjugate base; a base accepts a proton to form its conjugate acid.
- 4Lewis theory is the most general, defining acids as electron pair acceptors and bases as electron pair donors, encompassing reactions without H⁺ or OH⁻ transfer.
- 5All Brønsted-Lowry acids/bases are also Lewis acids/bases, but not vice versa (e.g., BF₃ is a Lewis acid but not Brønsted-Lowry).
⚠️ Common Mistakes
- ✕Confusing the scope and limitations of each theory, especially misapplying Arrhenius to non-aqueous reactions.
- ✕Incorrectly identifying conjugate acid-base pairs (e.g., adding/removing H⁺ from the wrong atom or incorrect charge adjustment).
- ✕Misidentifying Lewis acids (e.g., thinking all species with positive charge are Lewis acids; neglecting octet incompleteness or presence of vacant orbitals).
📝 Practice Questions
See allQ74.If 1 mM solution of ethylamine produces pH = 9, then the ionization constant (Kb) of ethylamine is 10−x . The value of x is ______ (nearest integer). [The degree of ionization of ethylamine can be neglected with respect to unity.]
Q61. Ksp for Cr(OH)3 is 1.6 × 10−30 . What is the molar solubility of this salt in water? (1) 1.8×10−30 (2) 5√1.8 × 10−30 27 × 10−30 (3) 4√1.6×10−3027 (4) 2√1.6
Q58.The molar solubility(s) of zirconium phosphate with molecular formula (Zr4+)3(PO3−4 )4 is given by relation : (1) Ksp 13 (2) Ksp 17 ( 9612 ) ( 6912 ) (3) Ksp 17 (4) Ksp 16 ( 8435 ) ( 5348 )
Q62.Which of the following happens when NH4OH is added gradually to the solution containing 1 M A2+ and 1MB3+ ions? Given : Ksp [A(OH)2] = 9 × 10−10 and Ksp [B(OH)3] = 27 × 10−18 at 298 K . (1) Both A(OH)2 and B(OH)3 do not show (2) A(OH)2 will precipitate before B(OH)3 precipitation with NH4OH (3) B(OH)3 will precipitate before A(OH)2 (4) A(OH)2 and B(OH)3 will precipitate together excess HCHO alkali−
Q68.pH of water is 7 at 25∘C. If water is heated to 80∘C., it's pH will : (1) Decrease (2) H+ concentration increases, OH− concentration decreases (3) Remains the same (4) Increase 2025 (23 Jan Shift 2) JEE Main Previous Year Paper
Q58.A weak acid HA has degree of dissociation x . Which option gives the correct expression of ( pH pKa )? (1) 0 (2) log(1 + 2x) (3) log ( 1−xx ) (4) log ( 1−xx )
NCERT Chapters
- Class 11 Chemistry Part 1 Ch 7: Equilibrium