BASES

BASES-

  • Bases have pH value greater than 7.
  • In solution, the base compounds conduct electricity.
  • Bases that are soluble in water are called alkalis. Example – NaOH, KOH, etc.
  • The strength of bases depends on the number of OH- ions produced.

On the basis of their strength, bases are classified as:

Strong Base

Weak Base

Base that gives rise to more OH- ions are said to be a strong base.

Base that gives less OH- ions are said to be weak base.

Examples of strong bases are sodium hydroxide (NaOH), barium hydroxide (Ba(OH)2), cesium hydroxide (CsOH), potassium hydroxide (KOH), etc.

 

Examples of weak bases are methylamine (CH3NH2), glycine (C2H3O2NH2), trimethylamine ((CH3)3N), hydrazine (N2H4), etc.

 

 On the basis of their concentration, bases are classified as:

  • Dilute bases: Have a low concentration of alkali in aqueous solutions
  •  Concentrated bases: Have a high concentration of alkali in aqueous solutions.

Uses of bases-

  • Sodium hydroxide is used in the manufacture of soap and paper. 
  • Calcium hydroxide is used in making cement, bleaching powder.
  • Magnesium hydroxide, popularly known as milk of magnesia. It is also used as an antacid since it decreases excess acidity in the human stomach.
  • Slaked lime can be used to neutralize any excess acidity in soils.

Chemical properties of Bases:

  • Reaction with Metals - Certain reactive metals such as Zinc, Aluminium, and Tin react with alkali solutions on heating and hydrogen gas is evolved. 2NaOH + Zn →  Na2ZnO+H2
  • Reaction with acids -Bases react with acids to form salt and water.  KOH +HCl → KCl +H2O
  • Reaction with Non -metallic oxides – These oxides are generally acidic in nature. They react with bases to form salt and water. 2NaOH + CO2 → Na2CO3 + H2O

 

Antacids:

  • The substance which work by counteracting or neutralizing excess amount of acid in the gastrointestinal tract is called an as antacid.
  • It is white crystalline solid and soluble in water.
  • It prevents Heartburn.
  • It also prevent from the ulcer (damage to lining of stomach wall, resulting in loss of tissues and inflammation).