CALCIUM (Ca)
Source
Chlorapatite – Ca5(PO4)3Cl
Phosphorite – Ca3(PO4)2
Fluorapatite – Ca5(PO4)3F
Fluorspar – CaF2
Anhydrite – CaSO4
Gypsum – CaSO4.2H2O
Dolomite – MgCO3.CaCO3
Extraction of Ca :
(1) By electrolysis of fused mixture of CaF2 and CaCl2 at 650ºC
CaCl2 → Ca+2 + 2Cl–
Electrolyte – CaF2 + CaCl2
Anode – Graphite
Cathode – Iron rod.
Reaction
Cathode → Ca+2 + 2e– → Ca
Anode → 2Cl– – 2e– → Cl2
(2) By reduction of CaCl2 with Al
3CaCl2 + 2A1 → 2AlCl3 + 3Ca
(3) By Gold Schmidt (Thermite) process
3CaO + 2Al → Al2O3 + 3Ca.
Properties of Ca :
(1) Greyish white crystalline metal with silvery lustre.
(2) Calcium reacts with oxygen to form calcium oxide
2Ca + O2 → 2CaO
(3) With hydrogen it reacts to form calcium hydride.
Ca + H2 → CaH2
(4) It readily reacts with chlorine to form calcium chloride
Ca + Cl2 → CaCl2
(5) On heating with nitrogen, calcium forms calcium nitride.
3Ca + N2 Ca3N2
(6) Due to its high oxidation potential it displaces H2 from H2O and dil acids
(A) Ca + 2H2O → Ca(OH)2 + H2
(B) Ca + 2HCl → CaCl2 + H2
(7) It reacts with carbondioxide on heating to form calcium oxide and calcium carbide.
5Ca + 2CO2
(8) It reduces Cr2O3 to chromium.
Cr2O3 + 3Ca → 3CaO + 2Cr
(9) It reacts with ammonia water at different temperatures to form different products.
Ca + 6NH3 → Ca (NH3)6
Ca (NH3)6
3Ca (NH2)2