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

Acid, Bases and Salts Class 10

Acid

• 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

Bases

• 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.

Dilute

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

Concentrated

• 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.

• This reaction is called a neutralization reaction.

Neutral

• Salts formed from strong acid and strong base are neutral

Acidic

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

For example:-

Bases

• 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.

Neutralization

• 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

Acids

• Electron pair acceptors are called acids.

Bases

• 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.