(I) When water is added to compound (A) of I calcium, solution of compound (B) is formed.
\(C\underset { (A) }{ a } O+{ H }_{ 2 }O\longrightarrow Ca\left( \underset { (B) }{ O } H \right) _{ 2 }\)
(ii) On passing Co₂ into compound b, it forms compound (c)
\(ca(OH)_{ 2 }+CO_{ 2 }\longrightarrow CaCO_{ 3 }+{ H }_{ 2 }O\)
(iii) If excess of Co₂ is passed to compound D is Formed 
\(CaCO_{ 3 }+{ H }_{ 2 }O+{ CO }_{ 2 }\longrightarrow Ca(HCO_{ 3 })_{ 2 }\)
(iv)  The milkiness disappears when excess of CO₂ is passed as soluble calcium bicarbonate is formed.

(i) Quick lime :
Preparation :
It is produced on a commercial scale by heating limestone in a lime kiln at 1173K (1070-1270).
\(CaCO_3\leftrightharpoons CaO + CO_2\)
Uses: Calcium oxide is used
(i) to manufacture cement, mortar and glass.
(ii) in the manufacture of sodium carbonate and slaked lime.
(iii) in the purification of sugar.
(iv) as drying agent
(ii) Slaked lime :
Preparation: Calcium hydroxide is prepared by adding water to quick lime, CaO.
CaO + H₂O ⟶ Ca(OH)₂
Uses: Calcium hydroxide is used
(I) in the preparation of mortar, a building material.
(ii) in white wash due to its disinfectant nature.
(iii) in glass making, in tanning industry, for the preparation of bleaching powder and for purification of sugar

(i) Sodium hydroxide is prepared commercially by the electrolysis of brine solution in Castner-Kellner cell .
(ii) Cathode- mercury
anode - carbon 
(iii) Sodium metal is discharged at the cathode and combines with mercury to form sodium amalgam.
(iv) Chlorine gas is evolved at the anode.
(v) The sodium amalgam thus obtained is treated with water to give sodium hydroxide
(vi) At cathode: Na⁺ + e^- ⟶ Na(amalgam)
At anode : Cl^- ⟶ 1/2 Cl₂ ↑ + e^-
2Na(amalgam) + 2H₂O ⟶ 2NaOH + 2Hg + H₂↑

(i) Monovalent sodium and potassium ions are found in large proportions in biological fluids.
(ii) maintenance of ion balance and nerve impulse conduction.
(iii) Sodium-potassium pump play an important role in transmitting nerv~ signals.
(iv) Sodium ions are found primarily on the outside of cells, being located in blood plasma and in the interstitial fluid which surrounds the cells.
(v) These ions participate iri the transmission of nerve signals, in regulating the flow of water across cell membranes and in the transport of sugars and amino acids into cells.
(vi) Sodium and potassium, although so similar chemically, differ quantitatively in their ability to penetrate cell membranes, in their transport mechanisms and in their efficiency to activate enzymes.
(viii)Thus, potassium ions are the most abundant cations within cell fluids, where they activate many enzymes, participate in the oxidation of glucose to produce ATP and, with sodium, are responsible for the transmission of nerve signals