Base

Base:

Those substance which give bitter taste and Slippery touch are known as Base.

  • Bitter taste.
  • Soapy touch.
  • Change red litmus to blue.

Example:

Soap, toothpaste, washing powder, Sodium Hydroxide (NaOH) , Calcium Hydroxide ( Ca (OH) 2 )  Aluminium Hydroxide    (Al (OH)3 )  , Potassium Hydroxide (KOH) etc.

  • According to Arrhenius Theory:

Those substance which gives hydroxide or hydroxyl ion ( OH-) in their aqueous solution are known as Base.

  • Alkali:

Base that completely  dissolve in water are called alkali.

Example:    KOH,  NaOH,  Ca (OH) 2 .

Imp- Note:

All the alkalis are base but All the bases are not alkalis.

Example: (Fe (OH)3 ) Ferric hydroxide,  and Cupric Hydroxide (Cu (OH)2) are base but not alkalis.

Classification of Bases:

1) Classification on the basis of their strength:

i) Strong Base or Alkalis:

The strong bases or alkalis which undergoes almost complete ionization in aqueous solution are known as strong bases or Alkalis.

Example:

NaOH (Sodium hydroxide) , KOH ( Potassium hydroxide) , Calcium hydroxide: Ca(OH); 2   ,Strontium hydroxide: Sr(OH); 2Barium hydroxide (Ba(OH)2) Caesium hydroxide (CsOH)

ii) Weak base:

The weak base or alkalis which undergoes only partial ionization in aqueous solution are known as weak base or alkalis.

Example:

LiOH, (lithium Hydroxide)  Be (OH) ( Beryllium hydroxide) etc.

2) Classification on basis of their Acidity:

Classification on the basis of their Acidity are three type i) monoacidic bases, ii) Diacidic bases iii) Triacidic bases

Acidity:  Acidity of base is number of hydroxyl or hydroxide (OH-) ion present in one molecule of base.

i) Monoacidic Bases:

The base or alkali complete ionization and produced one hydroxide or hydroxyl (OH-) ion are known as Monoacidic Bases.

Example: 

NaOH,   KOH,   CsOH etc.

ii) Diacidic bases:

The bases on complete ionization and produced two hydroxide or hydroxyl (OH-) ion are known as Diacidic bases.

Example:

Ba(OH) 2 ,  Be(OH) ,  Mg(OH) 2    etc.

iii) Triacidic Bases:

The bases on which complete ionization and produced three hydroxide or hydroxyl (OH-) ion are known as Triacidic bases.

Example:

Al(OH) ,  B(OH) ,  etc.

3) Classification on the basis of concentration of base:

i) Concentrated base:

The base which contains more amount of base and very small amount of water Is called a concentrated base.

ii) Dilute base:

The base which contains more amount of water and small amount of base are called Dilute base.

Question and Answers:

1) What is base?

2) Give the example of base?

3) Defined alkali with example?

4) Write the classification on the basis of their strength?

5) Write the classification on the basis of their acidity?

6) Defined acidity of base?

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