Railway Science (Chemistry-Chemical Reaction) (Part-IV)

An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two elements. Redox reactions are common and vital to some of the basic functions like photosynthesis, respiration, combustion, and corrosion or rusting. Oxidation - Loss of electrons, Hydrogen is lost or oxygen is gained. Example - 2Cu (Copper) + O₂ (Oxygen) → 2CuO (Copper Oxide).

In a double displacement reaction in which positive and negative ions of two ionic compounds exchange places. Example - 2K (potassium iodide) + Pb(NO₃)₂ (lead nitrate) → 2KNO3 (potassium nitrate) + Pb𝐼₂ (lead iodide). Ionic compound: type of compound formed from the electrostatic attraction between oppositely charged ions in a chemical compound.

When Barium chloride (3BaCI₂) reacts with aluminium sulphate {AI₂(SO₄)₃)} to give aluminium chloride (AICI₃) and a precipitate of barium sulphate (BaSO₄).
Barium sulphate starts functioning by coating Inside of your oesophagus, stomach, or intestines which allows them to be seen more clearly on a CT scan or other radiologic (x-ray) examination.

Oxidation - Loss of electrons by an atom, ion or molecule. Example - 2Zn(s) + O₂(g) → 2ZnO(s). In above reaction Zn metal is oxidized to ZnO.
Hydrolysis - Chemical reaction where water is mostly used to break down the chemical bonds that exist between a particular substance.
Reduction - Gain of electrons or a decrease in oxidation state by a molecule, atom or ion. Combination reaction - Two or more reactants combine to form a single product.

NaOH (strong base) + CH₃COOH (weak acid) → CH₃COONa + H2O. The resultant salt sodium acetate is basic in nature. NaCO₃ → NaO + CO₂ . It is a neutralization reaction that takes place between acid and base.

When barium chloride (BaCl₂) and sodium sulfate (Na₂SO₄) react, it leads to the formation of sodium chloride and barium sulphate. It is a Double displacement reaction and endothermic reaction. As a result of the above-given reaction, a white colour precipitate is formed due to the formation of barium sulphate.

Formation of sodium chloride - 2Na(s) + Cl₂(g) → 2NaCl(s). It is the chemical name for salt. Uses - Treat or prevent sodium loss caused by dehydration, excessive sweating.
Properties - Soluble in water and partially soluble or insoluble in other liquids, white crystals which do not have an odour but possess a taste, in its aqueous state NaCl acts as a good conductor of electricity due to the free movement of the ions.

When copper undergoes oxidation, it combines with oxygen to form copper oxide (CuO). This equation shows that two moles of copper (2Cu) react with one mole of oxygen (O₂) to form two moles of copper oxide (2CuO). Oxidation reaction in which electrons are transferred, a molecule loses electrons and the molecule that attains those electrons is said to be reduced.

Bleaching powder is produced by the action of chlorine on dry slaked lime Ca(OH)₂ . Chlorine is produced during the electrolysis of aqueous sodium chloride (brine), this chlorine gas is used for the manufacture of bleaching powder.
Calcium hypochlorite is the chemical name of bleaching powder. Bleaching powder is used as an oxidizing agent in many chemical industries Ca(OH)₂ + Cl₂ → CaOCl₂ + H2O.

Precipitation reaction: A chemical reaction occurring in an aqueous solution where two ionic bonds combine, resulting in the formation of an insoluble salt (precipitates). Example - AgNO₃(aqueous) + KCl(aqueous) → AgCl(precipitate) + KNO₃(aqueous).