this slides is about s block chapter three second year chemistry

2. Manufacture of Sodium or Extraction of
sodium
By Asghar Lashari

4. The cell is composed of and iron box lined
with fire bricks. The cell is fitted with a
central graphite anode and a surrounding
cathode the two electrodes are separated
by a cylindrical iron gauze diaphragm,
which screens the graphite anode from the
ring shaped iron cathode. This keeps away
the molten sodium metal from gaseous
chlorine.

5. In this process a mixture of NaCl and CaCl2
is electrolyzed. Ca Cl2 lowers the melting
point of NaCl from 801oC to 600oCNa is
collected at cathode and Cl2 at anode.
Some Ca ions are also Collected at cathode
but Ca being much denser than Na, does
not mix with it and cane be separated
easily.

6.  Reaction at cathode
 Reaction at anode
 Over all reaction

7.  OCCURRENCE
It occurs in nature as “rock salt” at
khewra, it also occur in sea water upto 3%.
It occurs in the form of “Brine” a super
saturated solution of NaCl from mines and
sea water.

8. It is obtained by solar evaporation of sea
water. The sea water contains Mg and Ca as
impurities. they are treated with to get Na Cl
PROPERTIES:
 It is colorless crystalline solid.
 It has a face centered cubic structure
 It is soluble in water
 It boiling point is 1440oC
 It reacts with H2 SO4 to produce HCl.

9.  It is an essential part of our daily diet
 It is used as food preservative.
 It is used in the manufacture of Na metal, Cl2
gas and other chemicals eg
 It is used in regeneration of water softener
and in salting out of soap.
 It is used in refrigeration in the form of
freezing mixture with ice.

10. This process is used to manufacture
following compounds.
 Sodium carbonate or soda ash, Na2CO3
 sodium carbonate deca hydrate or washing
soda Na2CO3 .10H2O and
 sodium hydrogen carbonate or baking soda
NaHCO3

11. Raw material used and their sources
 Brine or aq; NaCl: it is natural source of
NaCl
 CO2 it is obtained by heating limestone
 Ammonia : it is recovered from NH4 Cl

12. The process involves three steps.
 Ammoniation of Brine
 Carbonation of Ammoniated Brine
 Conversion to sodium carbonate

13.  Step No. 1:-
 In this step Brine (NaCl) is saturated with NH3 gas and is
allowed to flow down in ammoniating tower where the
flow controlled.
 Step No. 2:-
 In this step ammoniated brine is mixed with CO2 gas to
produce NH 4
+ and HCO3
- ions in carbonation tower.
NH3 + CO2 + H2O (NH4) 2CO3
(NH4)2CO3 + CO2 + H2O 2NH4HCO3
Then NH4HCO3 reacts with Na Cl (brine) to precipitate
less soluble NaHCO3 and NH4Cl. Lower part of tower is
coated and NaHCO3 is removed by vacuum filtration and
washed to free of ammonium salts.

14.  Step No. 3:- In this step Sodium
bicarbonate is heated to give anhydrous
sodium carbonate, which is called soda
ash.
 NaHCO3  Na2CO3 + CO2 + H2O
This soda ash is re-crystallized from hot
aqueous solution and washing soda
Na2 CO3.10H2O is formed.
Na2CO3 + 10H20  Na2CO3.10H20

16.  Reaction with carbon dioxide :
By passing CO2 through aqueous solution of Na2CO3
we get NaHCO3
Na2CO3+CO2 + H2O 2NaHCO3
 With silica (sand) : When Na2CO3 reacts with sand,
water glass is produced.
Na2CO3+SiO2  Na2SiO3+CO2
 With lime Ca(OH)2:- When Na2 CO3 reacts with lime
caustic Soda is obtained.
Na2CO3+ Ca(OH)2  CaCO3+NaOH

17.  It is used to manufacture water glass and as
water softener.
 It is used in making of soap, paper,
detergents, Na OH etc
 It is used in textile industry and petroleum
refinery.
 Sodium Hydrogen Carbonate (NaHCO3)
Baking soda

19.  Two chambers
 In first, chlorine is obtained and in second
caustic soda is formed
 Anode; Titanium or graphite
 Cathode; Flowing Mercury
 Electrolyte; Brine (saturated solution of
sodium chloride)

20. At anode;
2Cl-  Cl2
At cathode;
Na+ + e- Na
Na + Hg  Na/Hg (amalgam)
Na/Hg + H2O  NaOH + Hg + H2

21.  Efficient process and gives product of high
purity
 Possible reaction between chlorine and
caustic soda is avoided by using two different
chambers
 Mercury can be re-used
 Hydrogen can not be discharged at Hg
cathode due electrode potential difference

22.  In spite of strict control some mercury
vapous escape from plant and contaminate
the food chain
 It consumes large amount of electricity

23.  it is white crystalline Solid
 its Melting Point is 3220C
 it is highly soluble in water
 it has soapy touch even in dilute solution
and is bitter in taste.
 it is deliquescent and translucent solid

24.  With acid:-
it is strong alkali, turns red litmus paper blur and
neutralized to acids.
HCl + NaOH  NaCl + H2O
 With CO2 :-
Na OH absorbs atmospheric CO2 producing sodium
carbonate and H2 O
2NaOH + CO2  Na2 CO3 + H2O
 With Ammonium chloride: -
NaOH reacts with ammonium salt on warning and
librating ammonia.
NH4 Cl +NaOH NaCl +NH3 + H2O
 With FeCl3 :-
NaOH reacts with FeCl3 to give reddish brown ppt of
ferric hydroxide
3NaOH + FeCl3  Fe(OH)3 +3 NaOH

25.  it is used in preparation of Phosphine, Na
compounds.
 it is used in manufacture of soap, paper,
petroleum
 it is used in Purification of bauxite, in
bleaching dying process in mercerizing
(silky Finish) of Cotton and rayon

26.  Magnesium Sulphate Or (Epsom Salt)
MgSO4.7H2O
Hepta Hydrate Magnesium Sulphate
Gypsum (Calcium Sulphate dihydrate)
CaSO4.2H2O
Plaster of Paris (Calcium sulphate hemi
hydrte)
CaSO4.1/2H2O or (CaSO4)2. H2O
Bleaching Powder CaOCl2

27.  OCCURRENCE:-
 It occurs in nature as an ore which is
known as kieserite (MgSO4.H20)
 PREPARATION:-
 It is prepared by the action of sulphuric
acid with magnesium metal magnesium oxide
Mg (0H)2 magnesium carbonate.
 Mg + H2SO4 →MgSO4 +H2
 MgO + H2SO4 →MgSO4 +H2O
 Mg(OH)2 + H2SO4 →MgSO4 +2H2O
 MgCO3 + H2SO4 →MgSO4 +H2O + CO2

28.  PROPERTIES
 it is colorless crystalline solid.
 It is soluble in water
 When heated crystalline Epsom loses water
and form anhydrous magnesium sulphate.
 USES:-
 It is used in medicines as mild purgative
 It is used in the following industries
 (a) cement (b)soap (c)paper (d)ceramics
(e)cotton textile (f)dyes (g)paper

29.  OCCURANCE:-
 It occurs as anhydrous calcium
sulphate Ca SO4 and as dihydrate Ca SO4.
2H2O Gypsum is found in Pakistan in
abundance
 Properties
 It is sparingly soluble solid and produces permanent hardness in water.
At higher temperature gypsum loses all the water of crystallization to
give anhydrous calcium sulphate, on heating at 100oC it changes to
hemihydrate form called plaster of Paris.
 2[CaSO4 .2H2O] (CaSO4)2.H2O+3H2O

30.  USES:-
 Plaster of Paris when mixed with water, sets
in five minutes to a hard mass. This setting
takes place with expansion.
 This property permits to use in preparation
of moulds in surgery and castings.
 It is used for making plaster for walls
and floor

31.  EMPIRICAL FORMULA:-
 Professor Odling in 1861 suggested
empirical formula of bleaching powder as
CaOCl2 or Ca(OCl)Cl
 Preparation
 It is prepared by Hasen Clever plant
 Ca(OH)2 + Cl2  CaOCl2 + H2O

33.  Reaction with water
 CaOCl2 + H2O  Ca(OH)2 + Cl2
 Reaction with Hydrochloric acid
 CaOCl2 + HCl  CaCl2 + H2O + Cl2
 Reaction with moist Carbon dioxide:
 CaOCl2 + CO2 + H2O  CaCO3 + CaCl2 + HOCl
 USES:
 It is used in textile and other industries as an
oxidizing and bleaching agent.
 It is used in the purification of drinking water
 It is also used as disinfectant in showers and
drains