Discuss in brief Lewis concept of acids and bases.
Or
Discuss the electronic concept of acids and bases.
According to Lewis concept, an acid is any substance (atom, molecule or ion) which is capable of accepting a pair of electrons from another substance to form a co-ordinate (dative) bond.
A base is any substance (atom, molecule or ion) which is capable of donating a pair of electrons to form a co-ordinate (dative) bond. Hence,
In terms of electronic structure.
(i) an acid must have a vacant orbital into which an electron pair donated by a base can be accommodated e.g. AlCl3, BF3
(ii) a base is a substance which has at least one lone pair of electrons e.g
Comment on the statement: An acidic solution contains OH– ions and even a basic solution contains H3O+ ions.
Or
How the values of Kw, [H3O+] and [OH–] are affected if acid or base is added to pure water at 298K?
We know, [H3O+][OH–] = Kw
For pure water, [H3O+] =[OH–]
= 1 × 10–7 mol L–1
On adding few drops of an acid (say HCl) to water, the concentration of H3O+ increases and thus concentration OH– decreases accordingly in order to maintain Kw constant.
Hence acidic solution contains both hydronium and hydroxyl ions. But 
But on adding.
But on adding few drops of a base (say NaOH) to water, the concentration of OH–increases and thus the concentration of H3O+ decreases accordingly in order to maintain Kw constant.
Hence basic solution contains both hydronium and hydroxyl ions.
But [H3O+] < [OH–]
In general, in neutral solution,
[H3O+] = [OH–]
In acidic solution, [H3O+] > [OH–]
In basic solution, [H3O+] < [OH–]
Justify the statement: All Bronsted bases are Lewis bases, but all Bronsted acids are not Lewis acids.
What do you understand by ionic product of water?
All Arrhenius acids are Bronsted acids while all Arrhenius bases arc not Bronsted bases. Discuss.
All Arrhenius acids are Bronsted acids: According to Arrhenius, an acid is a substance that yields hydrogen ions in an aqueous solution. According to Bronsted concept, an acid is a substance that can donate a proton (H+ ion). Both definitions require an acid to be a source of protons. Thus HCl is an acid according to both the theories. Therefore, all Arrhenius acids are also Bronsted acids.
All Arrhenius bases are not Bronsted bases: According to Arrhenius concept, a base is a substance that dissociates in aqueous solution to give hydroxyl ions. According to Bronsted concept, a base is a substance that accepts a proton, e.g. NaOH is a base according to Arrhenius concept because it yields OH– ions in aqueous solution.
But NaOH does not accept a proton as such, thus it is not a base according to Bronsted concept. Therefore, all Arrhenius bases are not Bronsted bases.
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