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

Metals react with acid to give hydrogen gas and form metal salts. Zinc is more reactive than hydrogen. Reaction - Zn + H₂SO₄ (dil)→ ZnSO₄ + H₂ . In this reaction, Zn metal reacts with dilute H₂SO₄ to form ZnSO₄ and H₂ gas is liberated. Zinc (Zn, Atomic no. 30) and Sulphuric acid (H₂SO₄).

The loss of oxygen or the gain of hydrogen is called reduction. In reduction, the oxidation state of a molecule or an atom decreases. A substance that undergoes reduction is referred to as an oxidizing agent. Bromination - Any reaction which introduces a bromine atom into a compound.
Oxidation - A chemical reaction that takes place when a substance comes into contact with oxygen or another oxidizing substance. Chlorination is the process of adding chlorine to drinking water to kill parasites, bacteria, and viruses

Combination reaction: Two or more reactants combine to form a single product. Examples:- 2Ca + O₂ → 2CaO, CaO + H₂0 → Ca(OH)₂, etc.

Hydrogen gas (H₂) burns a matchstick with a pop sound. When electricity is passed through a concentrated solution of sodium chloride and water, which is called Brine, it decomposes and results in the formation of Sodium Hydroxide (NaoH), Chlorine gas (Cl₂ ), and Hydrogen gas (H₂).
2 NaCl (Sodium Chloride ) + 2 H₂O ( Water ) → 2 NaOH (Sodium hydroxide) + Cl₂ (Chlorine) + H₂ (Hydrogen).

Neutralisation and Precipitation reactions are the double displacement reactions. Example -
Na₂CO₃(Sodium carbonate) +
CaCl₂(Calcium Chloride) →
CaCO₃(Calcium Carbonate)↓ +
2NaCl(Sodium Chloride) is a precipitation reaction.

Electrolysis is the process where chemical energy can be converted to
electrical energy via the use of an electrical current on an electrolytic
solution. The electrolysis of brine solution to prepare sodium hydroxide can
be given as follows -
NaCl (conc.) ⇌ Na⁺ + Cl⁻, H₂O ⇌ H⁺ + OH⁻.
At cathode - 2H⁺ + 2e⁻ → H₂ ↑.
At anode - 2𝐶𝑙⁻ → Cl₂ ↑ + 2e-.
Na⁺ + OH⁻ → NaOH (Sodium hydroxide).
Bleaching Powder (CaOCl₂). Potassium
hydroxide (KOH). calcium hydroxide
(Ca(OH)₂).

Correct equation, H₂(g) + CO(g) → CH₂O (g) (Formaldehyde). Combination reaction - Single product is formed from two or more reactants. Examples - CaO + H₂O → Ca(OH)₂ (Calcium hydroxide).

CuS𝑂₄ (Copper Sulphate) + 𝐻₂S (Hydrogen Sulfide)→ CuS (Copper  Sulfide) + 𝐻₂S𝑂₂  (Sulfuric Acid).

Formation of Washing soda: Washing soda (Na₂CO₃) is synthesized through Solvay’s process. It involves the reaction of sodium chloride, ammonia and carbon dioxide in water; Carbon dioxide involved is produced through calcium carbonate and the calcium oxide left is used in recovering ammonia from ammonium chloride.
At first, sodium bicarbonate is obtained which is then converted to sodium carbonate on heating. Finally, washing soda is produced by recrystallization of sodium carbonate.
NaCl + NH₃ + CO₂+H₂O→NaHCO₃+ NH₄Cl 2 NaHCO₃ → Na₂CO₃ + H₂O + CO₂ Na₂CO₃ + 10H2O → Na₂CO₃ .10H₂O

Combination reaction: A type of reaction in which two or more elements or compounds (reactants) combine to form a single compound. Example; 2Na(s)+Cl₂ (g)→2NaCl(s).