S-Block Elements Test - 3

The inert pair effect is the tendency of the two electrons in the outermost atomic s-orbital to remain unionized or unshared in compounds of post-transition metals. This is because of the poor shieling by the electrons in the d and f subshells.

Alkali metals react vigorously with water and the reactivity increases down the group because both the ionisation energy of the alkali metals as well as the melting point decreases down the group.

Lattice energy increases from univalent solids like LiF to bivalent solids like MgS because the greater the charge on the ions. Hence, for the compounds of alkaline earth metals the lattice energy exceeds the enthalpy of hydration and consequently, the solubility in water decreases.

In the chlor-alkali industry, brine (mixture of sodium chloride and water) solution is electrolysed, producing chlorine (Cl₂), sodium hydroxide and hydrogen (H₂). The pure chlorine gas can be combined with hydrogen to produce hydrogen chloride.
Cl₂ (g) + H₂ (g) → 2HCl (g)
As the reaction is exothermic, the installation is called an HCl oven or HCl burner. The resulting hydrogen chloride gas is absorbed in deionised water, resulting in chemically pure hydrochloric acid. This reaction can give a very pure product. For example, for use in the food industry.

The bigger crystals of sodium chloride breaks up into smaller ones producing crackling sound called as decrepitation.
When the crystals are heated, they lose the water which becomes vapour and cracks the salt crystals as it escapes.

Soda ash is Na₂CO₃.
Na₂CO₃.10H₂O is washing soda.
NaOH is caustic soda.
NaHCO₃ is baking soda.

The most common alum is potash alum (K₂SO₄.Al₂(SO₄)₃.24H₂O).

Due to their high negative E° value (high reducing power) and extreme reactivity towards water, sodium and potassium cannot be isolated by reduction of oxides, metal displacement of their aqueous salt solutions or electrolysis of their aqueous salt solutions. Sodium and potassium can be prepared by the electrolysis of their fused chlorides.