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

A displacement reaction is a type of reaction that replaces part of one reactor with another. In the given reaction 2Al + Fe₂O₃ → 𝐴𝑙₂𝑂₃ + 2Fe   , Aluminium being more reactive than Iron, displaces Iron and results in the formation of the Aluminium oxide.

When balancing chemical equations, there should be an equal number of each atom on both sides. Combination reaction- Single product is formed from two or more reactants.
Decomposition reaction - A single substance decomposes to give two or more substances. 2NaCl (Sodium chloride)→ 2Na + Cl₂ and 2AgBr (Silver bromide) → 2Ag+ Br₂ .
Displacement Reaction - An element displaces another element from its compound. Fe + CuSO₄ (Copper sulphate)→ FeSO₄ (Iron sulphate) + Cu

A Combination reaction is a reaction where two or more elements or compounds combine to form a single compound. Example - CaO (Calcium Oxide) + H₂O (Water) → Ca(OH)₂ (Calcium hydroxide).
It is an exothermic reaction as a lot of heat is liberated with hissing sound during the reaction. Limestone - Calcium carbonate (CaCO₃).

Neutralization reaction - Acid and Base react to form Salt and Water. NaOH + CH₃COOH → CH₃COONa + H₂O. In this equation, acid is acetic acid and base is sodium hydroxide.
Salt (CH₃COONa) is formed. Sodium acetate (CH₃COONa) used as - additives in food, industry, concrete manufacture, heating pads and in buffer solutions.

Lead nitrate Pb(NO₃)₂ and potassium iodide (KI) react to form potassium nitrate (KNO3) and insoluble lead iodide (PbI₂). Chemical equation is:- Pb(NO₃)₂(aq) + 2KI (aq) PbI₂(s) + 2KNO₃  → (aq).
Precipitation Reaction - It is a type of chemical reaction in which two soluble salts in aqueous solution combine and one of the products is an insoluble salt called a precipitate.

Displacement Reaction - More reactive element displaces a less reactive element. Example: Fe(s) + CuSO₄(aq)→FeSO₄(aq) + Cu(s) . Cu (Atomic number - 29). CuSO₄ (copper sulphate). FeSO₄ (Ferrous sulphate).

It is an example of a double displacement reaction. Double replacement reactions - It is a reaction in which the positive and negative ions of two ionic compounds exchange places to form two new compounds. AB+CD→AD+CB.

Combination Reaction - A reaction in which two or more reactants combine to form a single product is known as a combination reaction. Such reactions are represented by equations of the following form: X + Y → XY. Calcium hydroxide (slaked lime) is formed by mixing water and calcium oxide. The reaction can be shown as: CaO + H₂O → Ca(OH)₂ . Calcium bicarbonate - Ca(HCO₃)₂ . Calcium carbonate - CaCO₃.

Silver chloride (AgCl) is a white crystalline solid that is well known for its low solubility in water. Uses of Silver chloride - Electroplating and mirror polishing, making alloys, poison antidotes, medicines, photographic films. etc. Boiling point (1,547 °C) and Melting point (455°C).

A displacement reaction is one wherein the atom or a set of atoms is displaced by another atom in a molecule. For instance, when iron is added to a copper sulphate solution, it displaces the copper metal.