Railway Science (Chemistry-Miscellaneous) (Part-II)

Glacial acetic acid (anhydrous acetic acid):- It contains a very low amount of water (less than 1%), which is used in cooking as vinegar and production of certain fragrances.
It is colorless and very corrosive in nature. It solidifies into solid acetic acid crystals just cooler than room temperature at 16.7 °C. Acetic acid (CH₃COOH) - It is a colorless liquid or solid compound, having a pungent characteristic odor.

Chemical equation - Representation of chemical reaction using symbols and formulae of the substances. Symbols used in chemical equation : + (used to separate multiple reactants or products), → (separates reactants from products), ⇌ ( for reversible reactions), Δ (reaction is being heated), (s) - Solid state, (l) - Liquid state, (g) - Gas state, (aq) - Aqueous solution (dissolved in water).

Dissolution - Process where a solute in gaseous, liquid, or solid phase dissolves in a solvent to form a solution. Examples - sodium chloride dissolving in water, water dissolving in 2-propanol to form rubbing alcohol, and zinc dissolving in copper to form brass, Naphthalene dissolves in kerosene, alkanes dissolves in organic solvents (benzene, carbon tetrachloride, and trichloroethylene), Gold and silver form amalgams with mercury.

Anion ions are formed when an atom gains electrons, it leads to the formation of negative ions known as anions. Example: Fluorine gains 1 electron to form F⁻ ions.
Cations ions are formed when an atom loses electrons, it leads to the formation of positive ions. Example : Sodium loses 1 electron to form Na⁺ ions.
Molecule is defined as the substance which is formed by the combination of the same type of atoms or different types of atoms. Example : H₂ , NaCl, etc. Neutrons, along with protons, are subatomic particles found inside the nucleus of every atom.

Winnowing - It is also used to remove pests or weevils from stored grain. Coagulation: The precipitation of colloids by removal of the charge associated with colloidal particles (Examples - yogurt, curdling of milk).
Sublimation: A process of conversion of a solid into vapor without passing through the liquid state (Examples - Iodine, Camphor, Ammonium Chloride, Naphthalene).
Filtration: The process of separating suspended solid particles from the fluid either by chemical or physical processes (Example - mixture of sand and water).

Copper sulphate (CuSO₄): Used as a fungicide, algaecide, root killer, antimicrobial. Bleaching powder [Ca(ClO)₂ ]: A pale yellowish powder used as a strong oxidizing agent in many industries.
Lime: A calcium-containing inorganic mineral used in the treatment of wastewater, water softening. Alum [KAl(SO₄)₂ ·12H₂O]:
Potassium alum is the most widely used alum and used in leather tanning, treatment of water as a flocculant, and treatment to fireproof textiles.

Sublimation - The transition of a substance directly from the solid phase to the gaseous phase without changing into the liquid phase.
Sintering - The process of forming a solid mass of material through heat and pressure without melting to the point of liquefaction.
Distillation is the process of converting a liquid into vapour, which then condenses into a liquid form. Distillation consists of both evaporation and condensation..

Sodium chloride is an ionic compound that consists of positively charged sodium ions (Na⁺) and negatively charged chloride ions (Cl⁻). The sodium atom loses one electron to form a positively charged ion (cation) with a stable electronic configuration of neon, while the chloride atom gains one electron to form a negatively charged ion (anion) with a stable electronic configuration of argon.

Neon (Ne) : Atomic number - 10. Filled with electrons (K shell with 2 electrons and L shell with 8 electrons). It is a noble gas. Uses - Vacuum lamps, lasers, advertising signboards, high voltage Indicators, cryogenic refrigerator, television tubes.
Electron configuration - Neon (1s²2s²2p⁶), Carbon (1s²2s²2p²), Magnesium (1s²2s²2p63s² ) and Argon (1s²2s²2p⁶3s²3p⁶).

Rust : An iron oxide (Fe₂O₃) usually reddish-brown oxide formed by the reaction of iron and oxygen in presence of water or air moisture. Ferric chloride (FeCl₃) : Orange to brown-black solid. Slightly soluble in water.
Ferric bromide (FeBr₃) : A red-brown odourless compound used as a Lewis acid catalyst in the halogenation of aromatic compounds. Ferric sulphide (Fe₂S₃) : A solid, black powder that degrades at ambient temperature.