CHEMISTRY (Part-V) (Railway)

2NaCl (aq) + 2H₂O (l) → 2NaOH (aq) + Cl₂ (g) + H₂(g)

• In Chlor-alkali process, an electricity is passed through an aqueous solution of sodium chloride or Brine (NaCl), which will decompose to form Sodium hydroxide (NaOH).

• It is called so because the products formed in this process are Chlorine (Cl) and Sodium Hydroxide.

• Here in this process, the term chlor stands for the product Chlorine and alkali is for Sodium Hydroxide.

Magnesium ribbon burns with a dazzling flame in air (or oxygen) and changes to white substance Magnesium Oxide (MgO).

• 2Mg + O → 2MgO

• Mg is oxidised to MgO in this reaction.

Atomic radius is defined as the distance from the centre of the nucleus of the atom to its outermost shell.

• Atomic radii of elements gradually increase in a group from top to bottom.

• As we go down a group, the atomic number increases. thus, the number of shells increases.

• Besides, as we move across a period from left to right, the atomic radii decrease gradually.

Carbon is able to form stable multiple bonds, i.e., single, double and triple bonds due to its small size.

• The small size enables the nucleus to hold on to the shared pairs of electrons strongly.

• The bonds formed by elements having bigger atoms are much weaker

A homologous series is a series of compounds of carbon that have different numbers of carbon atoms but have the same functional group.

• Each subsequent member of homologous series differs from the previous by one CH₂ unit.

• The difference between C₂H₆ (ethane) and C₃H₈ (propane) is CH₂ unit.

Bile salts helps in emulsification of fats, i.e., breaking down of the large fat droplets into very small micelles.

• Bile also activates lipase enzymes, which digests fats.

• Bile is produced by liver but stored and concentrated in the gall bladder.

Hydrogen gas and sodium hydroxide solution are produced

The sodium (Na, latin name Natrium) reacts with water very easily.

• It reacts with water to give a solution of sodium hydroxide and hydrogen gas with a large amount of heat. 2Na + 2H₂O→ 2NaOH + H₂

• Due to highly reactive Properties sodium stored in kerosene oil.

Alcohols react with sodium to evolve hydrogen gas, along with the formation of sodium alkoxides.

• Alcohol + Na → Sodium alkoxide + H₂

• Example: 2Na + 2CH₃CH₂OH → 2CH₂CH₂O-Na (Sodium ethoxide) + H₂ (g)

In a chemical reaction, a substance which loses oxygen or gains hydrogen is known as an oxidizing agent. The substance which gains oxygen or loses hydrogen is known as an reducing agent.

In the reaction Fe₂O₃ (s) + 2Al (s) → Al₂O₃ (s) + 2Fe, Ferric Oxide (Fe₂O₃) loses oxygen; so it acts as oxidisng agent. In contrast. Al gains oxygen; hence it is a reducing agent.

Non-metals form acidic oxides and are placed in group 16 of all the periods of the modern periodic table.

Example: Oxides of Sulphur.

• The group 16 elements of the modern periodic table consist of 5 elements oxygen, sulphur. selenium, tellurium, and polonium.