Question

Compare and contrast the Arrhenius, Bronsted-Lowry, and Lewis concepts of acids and bases.

Answer 1

	Arrhenius concept	Bronsted-Lowry concept	Lewis concept
Acid	An Arrhenius acid is a molecule that when dissolved in water will donate a proton (H+) in solution	A Bronsted-Lowry acid (like an Arrhenius acid) is a compound that breaks down to give an H+ in solution (solvent need not be water)	A Lewis acid refers to an atom or molecule that accepts an electron pair.
Base	An Arrhenius base is a molecule that when dissolved in water will break down to yield an OH- or hydroxide ion in solution	Bronsted-Lowry base refers to any atom or ion capable of accepting a free proton (H+) in solution	a Lewis Base is an electron pair donor
Example	Hydrochloric Acid (HCl) is an arrhenious acid as it can donate H+ in water Sodium hydroxide (NaOH) is an arrhenious base as it can donate OH- in water	HCl+NH3NH4+ + Cl- In this reaction HCl is an bronsted lowry acid (H+ donor) and Ammonia is a bronsted lowry base (H+ acceptor)	Simple cations like Ag+ , polar molecules like CO2, Molecules having a central atom with incomplete octet (like AlCl3) or central atom having empty d orbitals (like SiF4) can act as Lewis acids Neutral species with atleast one lone pair of electrons (like CH3OH) and anions like Cl- can act as lewis bases.

1. All arrhenious acids are bronsted and lowry acids but arrhenious bases (OH^- donor) are not bronsted-lowry bases (H⁺ acceptor).

2. Arrhenious concept covers only aqueous solutions, Bronsted Lowry concept cover non aqueous solutions also.

3. Bronsted Lowry concept covers ionic species also, unlike arrhenious concept which covers only neutral molecules.

4. Lewis cncept is too general and includes coordination compounds also.

5. Lewis concept doesnt explain the behaviour of known acids HCl, H₂SO_4.

6. Lewis concept doesnt explain the relative strengths of acids and bases.