CBSE Class 10 Chemistry Acids Bases And Salts Notes Set B

Acids: Substances which turn blue litmus solution red are called acids. Acids are sour in taste Bases: Substances which change red litmus solution blue are called bases. They are bitter in taste.
Mineral Acids: Acids which are obtained from minerals like sulphates, nitrates, chlorides etc. are called mineral acids, e.g., H₂SO₄(Sulphuric acid), HNO₃(Nitric acid) and HCl (Hydrochloric acid).
Organic Acids: Acids which are obtained from plants and animals are called organic acids.e.g. citric acid, ascorbic acid, tartaric acid, lactic acid, acetic acid. Hydronium Ions (H₃O + ): They are formed by reaction of H+ (from acid) and H₂O. It is because H+ is unstable.
Strong Acids: Acids which dissociate into ions completely are called strong acids. E.g. H₂SO₄, HCl
Weak Acids: Acids which do not dissociate into ions completely are called weak acids E.g. Citric acid, acetic acid.
Strong bases: The bases in which complete dissociation of hydroxide ions takes place are called Strong Bases. E.g. NaOH, KOH
Weak bases: The bases which do not dissociate completely in aqueous solution to form hydroxide ions are called weak Bases. E.g. NH₄OH

Chemical properties of acids
(i) Acids react with active metals to give salt and hydrogen gas.
(ii) Acids react with metal carbonate and metals hydrogen carbonate to give salt, water and carbon dioxide.
(iii) Acids react with bases to give salt and water. This reaction is called neutralization reaction.
iv) Acids react with metals oxides to give salt and water.

Chemical properties of Bases
(i) Reaction with Metals – Certain metals such as Zinc, Aluminum and Tin react with alkali solutions on heating and hydrogen gas is evolved
(ii) Reaction with acids – Bases react with acids to form salt and water

Indicators – Indicators are substances which indicate the acidic or basic nature of the solution by their color change.
Olfactory Indicator: Substances which change their smell when mixed with acid or base are known as Olfactory Indicators. For example; Onion, vanilla etc.
Onion: Paste or juice of onion loses its smell when added with base. It does not change its smell with acid.
Vanilla: The smell of vanilla vanishes with base, but its smell does not vanish with an acid.
Olfactory Indicators are used to ensure the participation of visually impaired students in the laboratory
Universal Indicator: A universal indicator is a mixture of indicators which shows a gradual but wellmarked series of color changes over a very wide range of change in concentration of H+ ion.
pH scale: A scale for measuring hydrogen ion concentration in a solution. The pH of a solution is defined as the negative logarithm of hydrogen ion concentration in moles per litre.

PH =-log [H+] pH =-log [H3O +] where [H+] or [H3O +] represents concentrations of hydrogen ions in solution. The pH of a neutral solution is 7 the pH of an acidic solution is < 7 The pH of a basic solution is> 7

Neutral, Acidic and Basic Salts:
(i) Neutral Salt: Salts produced because of reaction between a strong acid and strong base are neutral in nature. The pH value of such salts is equal to 7, i.e. neutral.
Example: Sodium chloride, Sodium sulphate. Potassium chloride, etc.
(ii) Acidic Salts: Salts which are formed after the reaction between a strong acid and weak base are called Acidic salts. The pH value of acidic salt is lower than 7. For example, Ammonium sulphate, Ammonium chloride, etc.
(iii) Basic Salts: Salts which are formed after the reaction between a weak acid and strong base are called Basic Salts. For example; Sodium carbonate Sodium acetate, etc.

The water of Crystallization: Many salts contain water molecule and are known as Hydrated Salts. The water molecule present in salt is known as Water of crystallization.
Examples:
Copper sulphate pentahydrate (CuSO₄.5H₂O): Blue color of copper sulphate is due to presence of 5 molecules of water. When copper sulphate is heated, it loses water molecules and turns: into grey – white colour, which is known as anhydrous copper sulphate. After adding water, anhydrous copper sulphate becomes blue again.

EQUATIONS OF ACIDS, BASES AND SALTS
1. Acid + Metal → Salt + Hydrogen gas- H₂SO₄+Zn → ZnSO₄+H₂
2. Base+ Metal → Salt + Hydrogen gas – Na₂ZnO₂ + H₂ → 2NaOH + Zn
3. Salt + Water → Base + Acid – NaCl (aq) + H₂O (l) → NaOH (aq) +HCl (aq)
4. Acids give hydronium ions in water- HCl+H₂O —>H₃O⁺ + Cl
5. Bases generate OH- ions in water NaOH(s)+H₂O → Na⁺ (aq)+OH^– (aq)