CHEMISTRY (Part-VI) (Railway)

When a solution of ethanol is heated with potassium permanganate (KMnO₄), the pink color of solution disappear because of strong oxidizing agent as KMnO₄, which oxidizes ethanol to ethanoic acid.

● CH₃CH₂OH (Ethanol) → CH₃COOH (Ethanoic acid)

● Alkaline potassium permanganate is a strong oxidising agent as it provides oxygen for oxidising other substances in the reaction. This reaction is known as the oxidation reaction.

K₂SO₄ is a salt of strong acid H₂SO₄ and strong base KOH.

● It is completely ionized in solution into K⁺ ions and SO₄²⁻ ions.

  K₂SO₄ ⇌ 2K⁺ + SO₄²⁻

● Thus, it is not hydrolyzed. Hence, its solution is neutral with pH 7.

In the given reaction of
2AgCl → 2Ag(s) + Cl₂(g), a single compound, i.e., AgCl breaks down when exposed to sunlight and produces different compounds :- Ag and Cl₂.

● Therefore, this reaction is a photo-decomposition reaction as well as endothermic reaction (heat is absorbed).

The chemical formula of Gypsum is (calcium sulphate dihydrate) CaSO₄.2H₂O.

● When gypsum is heated to a temperature of 100°C (373K), it loses three-fourths of its water of crystallisation and forms plaster of Paris (CaSO₄.1/2H₂O).

Newland's Law of Octaves asserts that when elements are grouped in increasing atomic mass order, the characteristics of the eighth element are the same as the first.

● The law of octaves was found to be applicable till calcium.

● After calcium, the properties of the next elements were not synchronous as per the law of octaves.

In the Mendeleev periodic table, there was no mention of noble gases like helium, neon, and argon.

● This is because they were not known at that time and were discovered much later.

● Since they are very inert gases they are present in extremely low concentrations in the atmosphere, so it was difficult to detect them with primitive technology.

Hydrogen reacts with nitrogen to form ammonia as:
N₂(g) + 3H₂(g) → 2NH₃(g)

● The reaction in which two or more reactant molecules combine to form one product is called as "combination reaction".

Acetic acid (CH₃COOH) has the highest boiling point among the given compounds.
This is because it forms a dimer with the help of intermolecular hydrogen bonding.

● Acetic acid which is dilute solution is used extensively as vinegar.

5 ml of HCl solution is required to neutralize 5 ml of NaOH.

• So as usual to neutralize 10 ml of same solution i.e., of NaOH we would need 5 × 2 = 10 ml of same solution of HCl.

Chlorofluorocarbon (CFCs), commonly known by the DuPont brand name Freon, are considered as one of the ozone-depleting substances (ODS).

• Because CFCs contribute to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol 1987.