s-Block Elements : EXTRACTION OF SODIUM (Na)

EXTRACTION OF SODIUM (Na)

Source :

      Rock salt                 –       NaCl

      Chile saltpetre       –       NaNO3

      Borax                      –       Na2B4O7. 10H2O

      Glauber’s salt        –       Na2SO4. 10H2O

 

Extraction:

(1) Down’s Process – By electrolysis of molten NaCl\

Electrolyte          – NaCl + CaCl2 or KF (at 600ºC)        

(Addition of CaCl2 and KF increases conductivity and decrease m.p. of the mixture).

            Anode      –       Graphite rod

            Cathode  –       Steel (Ring shaped)

Reactions:

          At anode –      Cl–  → Cl + e–

                                                          Cl + Cl → Cl2

          At cathode – Na+ + e– → Na

 

(2) Castner’s Process – By electrolysis of NaOH.

                              Electrolyte          –       NaOH (at 320ºC)

                              Anode                 –       Nickel cylinder

                              Cathode              –       Iron vessel

                    Reaction

                    At anode – 4OH– → 2H2O + O2 → + 4e–     

(Only O2 escapes out as gas)

                    At cathode –    Na+ + e– → Na

 

Properties of Na –

(1)     Soft silvery white metal

(2)     Na combines with air to form sodium oxide and sodium hydroxide

                              4Na + O2 → 2Na2 O

                              Na2O + H2O → 2 NaOH

(3)     Sodium displaces hydrogen from water, acids and alcohols

                              (A)    2Na + 2H2O → 2NaOH + H2

                              (B)    2Na + 2C2H5OH → 2C2H5ONa + H2

                                                                      (sodium ethanoate)

                              (C)    2Na + 2HCl → 2 NaCl + H2

 

(4)     When heated with hydrogen it forms metal hydride.

                              2Na + H2 \underrightarrow { \quad \quad 630\quad K\quad }   2NaH

(5)     It reacts with chlorine to form sodium chloride.

                              2Na + Cl2 → 2 NaCl

(6)     It reacts with sulphur to form sodium sulphide.

                              2 Na + S → Na2S

(7)     Sodium reacts with carbon dioxide to form sodium oxalate.

                              2Na + 2CO2 → Na2 C2 O4

(8)     With excess of CO2 it forms sodium carbonate and carbon.

                              4Na + 3CO2 → 2 Na2CO3 + C

(9)     It displaces hydrogen from Ammonia and forms sodamide.

                              2Na + 2NH3 \underrightarrow { \quad \quad 570-670\quad K\quad }   2NaNH2 + H2

(10)   It reacts with Al2 O3, displacing Aluminium

                              Al2 O3 + 6Na → 2 Al + 3 Na2O

(11)   It reacts with AlCl3 to give Al and NaCl

                              Al Cl3 + 3Na → Al + 3 NaCl