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What is Base | Definition of base in English by Fast2study

Base:

Bases are those substances which gives hydroxide ion in its aqueous solutions. Or,

Bases are those substance which has replaceable hydroxide ion (OH).

Example:- NaOH, KOH, RbOH, CSOH, Mg(OH)2, Ca(OH)2, Ba(OH)2, Sr(OH)2, Al(OH)3, NH4OH, CaO, MgO, LiOH, Zn(OH)2 .
What is Base | Definition of base in English by Fast2study

Note:-  The base (OH) of the element of first group are called as Alkalies because these bases are completely soluble in water that is completely water soluble bases are called Alkali. The metals which can found alkali are called as Alkali Metal.
Example:- Li, Na, K, Cs, Rb

According to Bronsted and Lowery Concept of Base:

Base is that types of substance which can accept proton donated by Acid.

According to Lewis Concept of Base:

Those substance which can donate lone pair of electron is called Lewis  Base.
Example:- CH3, CH3 - NH2, NH3, C6H6

Properties of Base:-

(i) It has bitter taste.
(ii) Generally base has property of smoothness like soap or detergent.
(iii)It changes red litmus paper to blue colour.
(iv) Generally bases are not Corrosive except NaOH and KOH.
(v) Strong bases are strong electrolyte why weak bases are weak electrolyte.
Alkali: A base which is soluble in water is called Alkali.

Types of Base:
    (1) Water soluble base (Alkali)
    (2) Water insoluble base

(1) Water soluble Base: Those type of base dissolve in water without any chemical reaction is called water soluble Base.

Example:- NaOH, KOH, RbOH, CSOH

(2) Water insoluble Base: Those type of base does not dissolve in water is called water insoluble Base.

Example:- Mg(OH)2Ca(OH)2, Ba(OH)2Sr(OH)2Al(OH)3, NH4OH .

Strong Base: A Base which completely ionises in water and produces a large amount of OH ions is called as Strong Bases.

Example:- NaOH, KOH.

Weak Bases: A base which partially ionised in water and produces a small amount of OH ions is called Weak Bases or Weak Alkali.

Example:- NH4OH, Ca(OH)2

Chemical Properties of Base:


(1) Reaction with Particular Metal: When base react with amphoteric metals like zinc and Aluminium then its form complex salt of basic metal with hydrogen gas.

Example:- 2Na(OH) + Zn Na2(ZnO2) + H2
Na(OH) + Al Na(AlO2) + H2

Amphoteric metal: Those metals whose oxide have acedic as well as basic nature is called Amphoteric metal.
Eg:- Zn, Al

(2) Reaction with Oxide of Non metal: When base react with non metal oxide to form salt and water.

Example:- Ca(OH)2 + CO2 CaCO3 + H2O
Ca(OH)2 + NO2 Ca(NO3)2 + H2O
Ca(OH)2 + SO2 CaSO4 + H2O

(3) Reaction with Acid: When base react with acid to form salt and water.
Example:- 2NaOH + H2SO4 Na2SO4 + 2H2O

Uses of Bases:

(i) Sodium hydroxide is used in the manufacture of soap, paper and rayon (synthetic fibre).
(ii) Calcium hydroxide is used in the manufacture of bleaching powder.
(iii) Magnesium hydroxide is used as 'antacid' to neutralize excess acid in the stomach and cure indigestion.

Detection of Carbon dioxide (CO2↑):

When CO2 react with lime water then colour of the product becomes milky white due to formation of calcium carbonate whose natural colour is milky white.
CO2↑ + Ca(OH)2 CaCO3 + H2O
When CO2 gas is passed through the solution of CaCO3 and H2O which has milky white colour then after the the completion of chemical reaction the milky white colour will be disappeared. Due to formation of colourless calcium bicarbonate.

CaCO3 + H2O + CO2 Ca(HCO3)2

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