Railway Science (Chemistry-Chemical Reaction)

(CuSO₄+Mg → MgSO₄ + Cu) - exothermic because energy is released in the reaction. When a piece of magnesium strip is added to some aqueous solution of CuSO₄ - a displacement reaction occurs where, Mg displaces Cu from its solution because more reactive metal displaces a less reactive metal from a compound. But Platinum and Silver are less reactive than copper. That is why they cannot displace It.

Displacement reaction - One element takes place with another element in the compound (A + BC → AC + B). Example - 2KI + 𝐶𝑙₂ → 2KCl + .  𝐼₂

The reaction conditions such as temperature, pressure, catalyst etc. are indicated above or below the arrow mark in the equation. Types of Chemical Reactions - Decomposition reactions, Single-replacement reactions, Double - replacement reactions.

Exothermic reaction - Produces energy in the form of light or heat i.e. Reactants → Products + Energy. So, the change in enthalpy ( ΔH) is negative. Examples - Combustion (Burning) - Burning of natural gas or methane in the presence of Oxygen (CH₄ + O₂ → CO₂ + H₂O + Heat).
Respiration - Taking oxygen and using it for combustion of glucose inside the body to produce energy (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy). Slaking of lime - When CaO is put in water, it forms calcium hydroxide and heat is produced (CaO + H₂O → Ca(OH)₂ + heat).

Balanced Chemical Equation - an equation where the number of atoms of each type in the reaction is the same on both reactants and product sides.
Example: Fe + H₂O → Fe₃O₄ + H₂ (after balancing - 3Fe + 4H₂O → Fe₃O₄ + 4H₂). C₅H₁₂ + O2 → CO₂ + H₂O (after balancing - C₅H₁₂ + 8O₂→ 5CO₂ + 6H₂O).

When magnesium is placed in copper sulphate solution a redox reaction occurs, causing copper metal to form on the magnesium and the deep blue colour of the solution pales.
Redox reaction: The substance getting reduced in a redox reaction is known as the oxidizing agent; while a substance that is getting oxidized is known as the reducing agent. Example – H₂ + F₂ → 2HF. The oxidation half-reaction is: H2 → 2H+ + 2e⁻ ; The reduction half-reaction is: F2 + 2e⁻ → 2F⁻ .

Reduced. Reduction: Gain of electrons; Hydrogen is gained or oxygen is lost. Example - CuO + H₂ → Cu + H₂O.
Oxidation: Loss of electrons; Hydrogen is lost or oxygen is gained. Example - 2Cu + O₂ → 2CuO.

Bleaching Powder Preparation - Bleaching powder is synthesized by the action of chlorine gas (Produced from the chlor - alkali process) on dry slaked lime {Ca(OH)₂}. Ca(OH)₂ + Cl₂ → Ca(OCl₂) + H₂O.
Uses - For bleaching dirty clothes in the laundry and as a bleaching agent for cotton and linen in the textile industry, used as an oxidizer in many industries, a disinfectant which is used for disinfecting water to make potable water.

Reduction - Gain of electrons, gain of Hydrogen or loss of oxygen.
Example - CuO (Copper oxide) + H₂ (Hydrogen) → Cu (Copper) + H₂O (Water). Oxidation - Loss of electrons, Loss of Hydrogen or gain of oxygen. An oxidizing agent tends to oxidize other substances. Example - 2Cu + O₂ → 2CuO.

Carbon reacts with Sulphur to give carbon disulphide, which is an endothermic reaction. S₈+ 4C → 4CS₂ . CS₂ (carbon disulphide): A colorless volatile liquid, Used as a building block in organic chemistry, an industrial and chemical non-polar solvent. It is highly flammable and its combustion gives out sulphur dioxide.