Class 10 Science Chapter 2 Acids, Bases and Salts Notes

1. Fundamental Differences

Acids: Sour in taste, turn blue litmus red, and release $H^+$ ions in aqueous solutions.
Bases: Bitter in taste, soapy to touch, turn red litmus blue, and release $OH^-$ ions in aqueous solutions.

2. Chemical Properties

Neutralization Reaction: Acid and base react together to form salt and water by neutralizing each other.

Acid + Base → Salt + Water
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
Reaction with Metals: Acids react with active metals to liberate Hydrogen gas.

Acid + Metal → Salt + Hydrogen Gas
2HCl(aq) + Zn(s) → ZnCl2(aq) + H2(g)↑

3. The pH Scale

A scale used for measuring hydrogen ion concentration in a solution. Range spans from 0 to 14.

pH < 7: Acidic solution (0 is highly acidic).
pH = 7: Neutral solution (Pure water/blood).
pH > 7: Basic solution (14 is highly alkaline).

4. High-Yield Commercial Salts

Bleaching Powder ($CaOCl_2$): Produced by action of chlorine on dry slaked lime. Used as a disinfectant.
Plaster of Paris ($CaSO_4 \cdot \frac{1}{2}H_2O$): Obtained by heating Gypsum at 373K. Hardens into solid gypsum when mixed with water.

CBSE Concept Check

Why does dry HCl gas not change the color of dry litmus paper? Litmus paper only changes color when it encounters $H^+$ ions. Dry HCl gas cannot dissociate into ions without an aqueous medium. It needs moisture/water to show its acidic nature!

✏️ Complete NCERT Solutions Class 10 Chapter 2

Q1. Why should curd and sour substances not be kept in brass and copper vessels?

Answer: Curd and sour substances naturally contain organic acids. These acids react chemically with metals like copper and brass to form toxic, poisonous organic metal salts. Eating food stored in these corroded vessels can cause severe food poisoning.

Q2. While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

Answer: Mixing concentrated acid with water is an extremely highly exothermic process. If you add water directly into concentrated acid, the sudden massive flash of heat can boil the water instantly, causing the dangerous acid mixture to splash out onto your face and clothes, or shatter the glass container. Adding acid slowly to a large pool of water allows the water to absorb and distribute the heat safely.

CBSE Class 10 Science Chapter 2: Acids, Bases and Salts

1. Fundamental Differences

2. Chemical Properties

3. The pH Scale

4. High-Yield Commercial Salts

✏️ Complete NCERT Solutions Class 10 Chapter 2