Strength, Preparation And Properties Of Acids And Bases

BASES / ALKALI

Bases:
*Substances with sticky nature and changing red litmus into blue an called as bases.
*The substance which react with acids to form salt and water as the only products are called bases.
*All oxides and hydroxides of metals are bases.
*A base is a substance which dissolves in water to produce bases are chemically opposite to acids. Which produces hydroxide ions (OH^-) in aqeous solution.
*The name of all bases start with the name of a metal and end with the oxide or hydroxide.

Alkali :
A base which is soluble in water is called as an alkali. The word alkali came from Arabic means ash. Long ago people burnt plants and used the ashes in making soaps and glass. The ashes contained the alkalis soda and potash.
Ex: Sodium hydroxide (NaOH),  Potassium hydroxide (KOH)
All alkali can be bases but all bases are not alkalis. However as it dissolves in water to furnish ions (OH^-), hence it is an alkali.

Based on strength
Strong alkali :-    
The alkalis which almost completely dissociates in an aqueous solution to produce high concentration of hydroxyl (OH^-) ions are called as strong alkalis.
            KOH     \( \rightleftharpoons \)      K⁺+OH^-
    
Weak alkali :-
The alkalis which undergo partial dissociation in an aqueous solution so as to produce low concentration of hydroxyl ions are called weak alkalis.
            NH₄OH    \( \rightleftharpoons \)   NH₄⁺+OH^-
Ex:Ca(OH₂), Mg(OH)₂  

Concentrated alkali :-
An alkali solution having a relatively high percentage of alkali in its aqeous solution is called concentrated alkali.

Dilute alkali :-
An alkali solution having relatively less percentage of alkali in its aqeous solution is called dilute alkali.