Acid, Base and Salts RRB PYQ

Sodium hydroxide is the primary alkali product formed in the chlor-alkali process. The process involves the electrolysis of a concentrated aqueous solution of sodium chloride, commonly known as brine. The term 'chlor-alkali' is derived from the two main products: chlorine produced at the anode and an alkali produced near the cathode. The overall chemical reaction for this process is: 2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g).

Gypsum is the substance used in the preparation of calcium sulphate hemihydrate. Calcium sulphate hemihydrate (CaSO4·(1/2)H2O) is the chemical name for Plaster of Paris (POP). It is produced by heating gypsum (CaSO4·2H2O) to a specific temperature of 373 K in a kiln. At this temperature, gypsum loses three-quarters of its water of crystallization to become the hemihydrate powder.

Non-metallic oxides are generally acidic in nature because they react with water to form acidic solutions. Because they are acidic, they react with bases to produce salt and water, a process similar to the neutralization reaction between an acid and a base. In contrast, most metallic oxides are basic in nature and react with acids to form salt and water. Non-metallic oxides of sulfur and nitrogen released from factories react with rainwater to form acid rain, which has a pH lower than 5.6.

Oxygen gas is not formed when electricity is passed through an aqueous solution of sodium chloride. This electrolytic process is named after its primary products: chlorine and an alkali. During electrolysis, chlorine gas is released at the anode, while hydrogen gas is released at the cathode. Sodium hydroxide solution is formed near the cathode, as the sodium ions react with the hydroxide ions remaining in the water.

Salt and hydrogen gas are produced when an acid reacts with a metal. This chemical reaction follows the standard pattern: Metal + Dilute Acid → Salt + Hydrogen gas. The metal displaces hydrogen from the acid, provided the metal is more reactive than hydrogen in the reactivity series. Generally, metals do not produce hydrogen gas when reacting with nitric acid because it is a strong oxidizing agent that oxidizes the hydrogen into water instead.