Solution of Acid, Bases and Salts | NCERT Class 10 Science

Acid, Bases & Salts

Acid, Bases and Salts Class 10


  • sour in taste.
  • “Acid” is taken from latin word “acidus” which means sour.
  • It turns blue litmus paper into red.
  • PH of less than seven.
  • For example:-
    • Acetic acid, amino acid, citric acid, hydrochloric acid, lactic acid, nitric acid, sulphuric acid etc.
    • Vinegar : acetic acid
    • Tamarind : tartaric acid
    • Orange : ascorbic acid
    • Sting of red Ant : formic acid


  • Bitter in taste.
  • It turns red litmus paper into blue.
  • They are soapy to touch.
  • For example:- 
    • Sodium hydroxide (NaOH),
    • Potassium hydroxide (KOH),
    • Ammonium hydroxide (NH₄OH) etc.
    • Acids and bases are soluble in water.


  • If they contain a high quantity of water then acid/base are called dilute.


  • If they contain a high quantity of acid/base then water, they are called concentrated.

Neutralization Reaction

  • Acid and base on reaction and form salts and water.
Neutralization Reaction
  • This reaction is called a neutralization reaction.


  • Salts formed from strong acid and strong base are neutral


  • Salts formed from strong acid and weak base are acidic.

For example:-



  • Salts formed from weak acid and strong bases are bases.

For example:-

  • Melting point and boiling point of salts are high.

Water of crystallization

  • The number of water molecules attached with the unit formula of salts is called water of crystallization.
  • It means when the salts crystallize, the water evaporates.
  • For example:-
    • Na₂CO₃.10H₂O
    • Where, 10 molecules of water are present in the form of water of crystallization in sodium carbonate salts.

Arhenius theory

  • According to Arhenius theory
  • The substances which give hydrogen ions
  • (H+) on hydrolysis in aqueous solution are
  • called acid and the substances which give
  • hydroxyl ions (OH) on hydrolysis in aqueous
  • solutions are called bases.
  • Examples of acid:
  • These are all acids because they give (H+) ions in aqueous solution.
  • Hydrogen ion (H+) is more reactive.

Strong Acids

  • Acids are completely ionized in aqueous solution, such acids are called strong acids.
  • For example:
    • HCL, H₂SO4, HNO₃ etc.

Weak Acids

  • Acids are not completely ionized in aqueous solutions, such acids are called weak acids.
  • For example:-
    • CH₃COOH, H₂CO₃ etc.
    • Example of bases
  • These are all bases because they give
  • hydroxyl ions (OH) in an aqueous solution.

Strong Bases

  • Which are complete, ionized in aqueous solution, are called strong bases.
  • For example:
    • KOH, NaOH etc.

Weak bases

  • which are not completely ionized in aqueous solution, are called weak bases.
  • For examples:
    • NH4OH, Mg (OH)2 etc.


  • On reaction of acids and bases, H+ and OH ions combine to form water. This reaction is called neutralization.
  • It liberates heat so it is exothermic in nature.
  • For example:

Note :- Hydrolysis: –

  • Hydrolysis is a common form of a chemical reaction where water is mostly used to break down the chemical bonds that exists between a particular substance.
  • Hydrolysis is derived from a Greek
  • word hydro meaning water and lysis which
  • translates to the word-break / to unbind.
  • hydrolysis the water molecules get attached to two parts of a molecule.
  • One molecule of a substance will get
  • H+ ion and the other molecule receives the OH group.
  • Hydrolysis reaction is mainly used to break down polymers into monomers.

Note: – Aqueous Solution

  • An aqueous solution is a solution in which the solvent is water.

Bronsted – Lowry concept of Acids and Bases

  • According to Bronsted – Lowry “Acids are proton donor and bases are proton acceptor.”
  • When an acidic substance loses a proton, it forms a base, called the conjugate base of an acid.
  • When a basic substance gain a proton, it forms an acid called the conjugate acid of a base.
  • For example:
  • Here, H₂O donates proton so, it is acid and
  • converts in to conjugate base (OH) by
  • donating proton.
  • Ammoria (NH3) is proton acceptor.
  • So it is base.
  • It converts into conjugate acid (NH4+) ammonium ion by accepting proton
  • These pairs are called conjugate acid-base pairs.

Lewies Concept of Acids and Bases

  • According to lewis concept, “acids are those substances which accept electron pairs and bases are those substance which donate give up electron pairs”. Or


  • Electron pair acceptors are called acids.


  • Electron pair doners are called bases.

For example

  • Reaction between BF3 and NH3

According to this concept –

Lewis Acid

  • The compounds having electron deficiency will act as acids, are called lewis acid. In other word says, cation or those compounds which have incomplete octet are called lewis acids.
  • For example– BF3, Ca2+, Na+, Mg2+ etc.

Lewis Base

  • Electron rich or the compounds
  • having lone pair of electrons act as bases,
  • there are called lewis base.
  • For example- H₂O, NH₃, OH,  Cl etc.


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