INDUSTRIAL PREPARATION OF SODIUM CARBONATE
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On industrial scale sodium carbonate is prepared by Ammonia Solvay Process.
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Raw Materials
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1. Sodium Chloride 2. Lime Stone (CaCO3) 3. Ammonia |
Details of the process
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At first stage a saturated solution of sodium chloride is prepared which is also known "BRINE". Composition of solution of NaCl (brine) is 28% m/m. |
Steps of preparation
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Ammoniation of Brine
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In this stage saturated brine is allowed to flow down an ammoniating tower. This tower is fitted with mushroom shaped baffles. These baffles control the flow of brine and ensure the proper mixing and saturation of ammonia. |
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Carbonation of ammoniated brine
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In the second step, ammoniated brine is allowed to trickle down a carbonating tower known as solvay tower. This tower is also fitted with baffle plates. Here brine is mixed with carbon dioxide gas, produced by heating lime stone in a separate chamber called "kiln". |
CaCO3 è CaO + CO2
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the baffle plates ensure the flow of solution and breaks up carbon dioxide into small bubbles to produce good conditions for reaction. |
Flow Chart
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Chemistry of Solvay tower
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CO2 reacts with ammonia to form ammonium carbonate. |
2NH3 + CO2 + H2O è (NH4)2CO3
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Ammonium carbonate further reacts with CO2 to form ammonium bicarbonate. |
(NH4)2CO3 + CO2 + H2O è 2NH4HCO3 (aq.)
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Ammonium bicarbonate then react with NaCl to form sodium bicarbonate. |
NH4HCO3 + NaCl è NaHCO3 + NH4Cl
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Due to exothermic nature of above reactions, solubility of NaHCO3 increases. To counter this effect , lower part of Solvay tower is cooled , ppt of NaHCO3 are separated by vacuum filtration and washed to remove ammonium salts. |
Conversion of NaHCO3 to Na2 CO3
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Dry sodium bicarbonate is heated in rotary furnace called "CALCINER" to give anhydrous sodium carbonate or soda ash. Carbon dioxide is re circulated to carbonation tower. |
2NaHCO3 è Na2 CO3 + CO2 + H2 O
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Ammonia recovery process
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When CaCO3 is heated, CaO is obtained along with CO2 . CaO is treated with water to form Ca(OH)2 . |
CaO + H2 O è Ca(OH)2
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Quick lime is heated with NH4 Cl to form NH3 and calcium chloride (by product) . Ammonia is used again in this process. |
2NH4 Cl + Ca(OH)2 è CaCl2 + 2NH3 + 2H2 O
INDUSTRIAL PREPARATION OF SODIUM HYDROXIDE
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SODIUM HYDROXIDE
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Chemical formula : NaOH Chemical name : sodium hydroxide Commercial name : caustic soda |
RAW MATERIALS USED IN THE PREPARATION
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Sodium chloride (NaCl). Water (H2O). |
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PRINICIPLE
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Sodium hydroxide is a strong base and is prepared by the electrolysis of aqueous solution of sodium chloride known as brine. |
METHOD
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PREPARATION OF BRINE: NaCl is mixed in water to produce brine. Composition of brine is 25% m/m. |
ELECTROLYSIS OF BRINE
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Electrolysis of brine is carried out in an electrolytic cell known as "Diaphragm cell". When an electric current is passed through the brine, following changes take place. |
Ionization of NaCl: 2NaCl ® 2Na+ + 2Cl- |
Ionization H2O: 2H2O ® 2H+ + 2OH- |
Electrochemical changes
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At cathode: 2H+ + 2e- ® H2 At anode: 2Cl- ®Cl2 + 2e- |
During electrolysis, Na+ ions are not discharged but H+ ions are readily discharged. As more H+ ions are discharged, more H2O dissociates to replace it. Na+ and OH- ions accumulate in the solution. On evaporation sodium hydroxide is obtained. Na+ + OH- ® NaOH
WATER GAS-INDUSTRIAL PREPARATION OF HYDROGEN GAS
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WHAT IS WATER GAS? |
A mixture of carbon monoxide and hydrogen gas is commonly known as water gas. [CO + H2] ® water gas It is used as a fuel. PREPARATION: It is prepared by passing steam over red hot coke. C + H2O ® CO + H2 |
WHAT IS WASHING SODA? |
Sodium carbonate deca hydrated (Na2CO3.10H2O) is commonly known as washing soda. |
WHAT IS BAKING SODA? |
Sodium bicarbonate NaHCO3 is commonly known as baking soda. |
WRITE DOWN INDUSTRIAL PREPARATION OF HYDROGEN GAS? |
Hydrogen gas can be prepared by a lot of methods. Some important are as under.
BY THERMAL DECOMPOSITION OF METHANE:
When natural gas is heated up to 1000oC in the presence of catalyst, hydrogen gas is obtained.
CH4 ®C + 2H2
BY COKE AND STEAM PROCESS:
When super heated is passed over red hot coke, a mixture of carbon monoxide and hydrogen is obtained which is known as water gas.
C + H2O ®CO + H2
By liquefication method pure hydrogen is separated.
BY THE ELECTROLYSIS OF WATER:
When pure water containing a little amount of H2SO4 or any ionic salt is electrolyzed, pure hydrogen is obtained.
LANE’S METHOD:
When steam is passed over red hot iron, hydrogen gas is obtained.
3Fe + 4H2O ®Fe3O4 + 4H2
BY THE THERMAL DECOMPOSITION OF AMMONIA:
When ammonia gas is strongly heated it decomposes in to nitrogen and hydrogen.
2NH3 ® N2 + 3H2
N2 gas is separated by liquefication method.
WHAT IS THERMITE PROCESS? |
THERMITE PROCESS: Reduction of metal oxides by aluminum is called thermite process. In this process a huge amount of heat is liberated which causes a temperature up to 3000oC. Due to this reason thermite process is used for welding of broken metal parts. 2Al + Fe2O3 ® Al2O3 + 2Fe + Heat |
WHAT IS PLASTER OF PARIS? HOW IT IS PREPARED? WRITE ITS PROPERTIES? |
CHEMICAL NAME: Calcium Sulphate Hemi Hydrated CHEMICAL FORMULA: CaSO4.1/2H2O or (CaSO4)2.H2O COMMERCIAL NAME: Plaster Of Paris
METHOD OF PREPARATION: When gypsum is heated to 100oC, it loses water molecules to produce plaster of Paris. |
2(CaSO4.2H2O) ® (CaSO4)2.H2O + 3H2O
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PROPERTIES |
When plaster of Paris is ground to fine powder and mixed hard forming gypsum again. The setting results with expansion so the plaster of Paris fits tightly in to mold. |
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