Caustic Soda Or NaOH (Castner Kellner's Process)
Introduction
Caustic Soda or Sodium Hydroxide is one of the most important chemicals of industrial use. Caustic Soda must be handled carefully because it is caustic to touch and causes painful burns.
Castner Kellner's Process
Caustic Soda is manufacture by an electrolytic process. This process is carried out in an electrolytic cell known as Castner-Kellner's cell and the process is called Castner-Kellner's Process.
Construction Of Castner-Kellner's Cell
The electrolytic solution is a 25% of NaCl solution. The anode consist of a number of titanium plates whereas cathode is a steam of flowing mercury.
Diagram Coming Soon
Working of Castner-Kellner's Cell
Sodium chloride dissociates in water to give Na+ and Cl- ions are
2NaCl ----> 2Na+ + 2Cl-
The Cl- ions migrate towards titanium plates, it gains electron and convert into chlorine gas.
2Cl- ----> Cl2 + 2e- (Oxidation)
In castner-kellner's process, H+ ions are not easily discharged due to high voltage of H+ ions, on the contrary Na+ ions are easily discharge over mercury surface. The sodium, thus liberated dissolves in mercury forming an amalgam.
2Na+ + 2e- ----> 2Na (Reduction)
Na + Hg ----> Na/Hg (Amalgum)'
The mercury containing dissolved sodium is sent to another chamber called Denuder where sodium reacts with water forming sodium hydroxide and hydrogen. Denuder is packed with graphite blocks as hydrogen is easily liberated over graphite surface.
2Na/Hg + 2H2O ----> 2NaOH + H2 + 2Hg
The mercury is recycled to dissolve more of sodium.
The solution, which flows out from denuder, is a NaOH solution, which is evaporated to dryness.
Showing posts with label Class XII (BIEK) Notes. Show all posts
Showing posts with label Class XII (BIEK) Notes. Show all posts
XII Chemistry BIEK Topic - Sodium (Down's Process)
Sodium (Down's Process)
Introduction
On large scale, sodium is manufactured by electrolysis of fused sodium chloride. The process was given by scientist Dawn, therefore, it is called Dawn's Process.
Construction of Down's Cell
A special electrolytic cell known as Dawn's cell is used for the electrolysis of sodium carbonate. The cell consists of a cylindrical shape iron basin lined inside by firebricks. The iron cathode is separated from anode by iron gauze diaphragm. Anode consists of a carbon rod, which is present between two iron cathodes. The electrolytic solution consists of a mixture of sodium chloride (NaCl) and calsium chloride (CaCl2). Calsium Chloride (CaCl2) is added to decrease the melting point of sodium chloride from 801ºC to 600ºC.
Working of Dawn's Cell
When electric current is passed through molten NaCl, the sodium ion migrates towards cathode. It gains and electron and converts into molten sodium metal, which floats inside the cathode compartment. This molten sodium metal is allowed to pass through pipe 'p' which collects it in a vessel 'V' outside the cell.
Introduction
On large scale, sodium is manufactured by electrolysis of fused sodium chloride. The process was given by scientist Dawn, therefore, it is called Dawn's Process.
Construction of Down's Cell
A special electrolytic cell known as Dawn's cell is used for the electrolysis of sodium carbonate. The cell consists of a cylindrical shape iron basin lined inside by firebricks. The iron cathode is separated from anode by iron gauze diaphragm. Anode consists of a carbon rod, which is present between two iron cathodes. The electrolytic solution consists of a mixture of sodium chloride (NaCl) and calsium chloride (CaCl2). Calsium Chloride (CaCl2) is added to decrease the melting point of sodium chloride from 801ºC to 600ºC.
Working of Dawn's Cell
When electric current is passed through molten NaCl, the sodium ion migrates towards cathode. It gains and electron and converts into molten sodium metal, which floats inside the cathode compartment. This molten sodium metal is allowed to pass through pipe 'p' which collects it in a vessel 'V' outside the cell.
XII Chemistry BIEK Topic - Sodium Carbonate (Ammonia-Solvay Process)
Sodium Carbonate (Ammonia-Solvay Process)
Introduction
Sodium Carbonate is an important compound. It is manufactured by Ammonia-Solvay Process.
Raw Meterials
The raw materials for the manufacture of sodium carbonate are
1. Brine
2. Ammonia, which is made by Haber's Process
3. CO2, CaOH, which are obtained from limestone.
Ammonia-Solvay Process
The Ammonia-Solvay Process consist of the following steps.
Step I - Ammonation of Brine
In first step, ammonia gas is mixed with brine. This process is carried in Ammonation Tower. The ammonation tower consist of mushroom shaped buffels at short intervals. Brine is introduced from the top and ammonia is introduced from bottom. They both flow towards each other. Buffels control the flow of brine and ensure that they are mixed to the point of saturation with ammonia.
Step II - Carbonation of Ammonated Brine
In this step, ammonated brine is mixed with carbon dioxide brine is mixed with carbon dioxide in a tower called carbonating tower or Sonvai tower. Ammonated Brine is fed from the top where as carbon dioxide ascends from the bottom. When these two substances meet, the following chemical reactions takes place.
2NH3 + CO2 + H2O ----> (NH4)2CO3
(NH4)2CO3 + CO2 + H2O ----> 2NH4HCO3
2NH4HCO3 + NaCl ----> NaHCO3 + NH4Cl
Sodium bicarbonate is relatively insoluble, which is precipitated out from the solution by cooling the lower part of the tower. Sodium bicarbonate is separated from soluble ammonium chloride by vacuum filteration.
Step III - Production of Soda Ash
Sodium bicarbonate is heated in a long iron tube to obtain anhydrous sodium carbonate or Soda Ash.
This carbon dioxide is recycled to the solvay tower. This hydrated sodium carbonate is also called washing soda.
Recovery of Ammonia
Ammonia gas is recovered from the remaining solution by treating it with Calsium Hydroxide.
2NH4Cl + Ca(OH)2 ----> CaCl2 + 2H2O + NH3
Introduction
Sodium Carbonate is an important compound. It is manufactured by Ammonia-Solvay Process.
Raw Meterials
The raw materials for the manufacture of sodium carbonate are
1. Brine
2. Ammonia, which is made by Haber's Process
3. CO2, CaOH, which are obtained from limestone.
Ammonia-Solvay Process
The Ammonia-Solvay Process consist of the following steps.
Step I - Ammonation of Brine
In first step, ammonia gas is mixed with brine. This process is carried in Ammonation Tower. The ammonation tower consist of mushroom shaped buffels at short intervals. Brine is introduced from the top and ammonia is introduced from bottom. They both flow towards each other. Buffels control the flow of brine and ensure that they are mixed to the point of saturation with ammonia.
Step II - Carbonation of Ammonated Brine
In this step, ammonated brine is mixed with carbon dioxide brine is mixed with carbon dioxide in a tower called carbonating tower or Sonvai tower. Ammonated Brine is fed from the top where as carbon dioxide ascends from the bottom. When these two substances meet, the following chemical reactions takes place.
2NH3 + CO2 + H2O ----> (NH4)2CO3
(NH4)2CO3 + CO2 + H2O ----> 2NH4HCO3
2NH4HCO3 + NaCl ----> NaHCO3 + NH4Cl
Sodium bicarbonate is relatively insoluble, which is precipitated out from the solution by cooling the lower part of the tower. Sodium bicarbonate is separated from soluble ammonium chloride by vacuum filteration.
Step III - Production of Soda Ash
Sodium bicarbonate is heated in a long iron tube to obtain anhydrous sodium carbonate or Soda Ash.
This carbon dioxide is recycled to the solvay tower. This hydrated sodium carbonate is also called washing soda.
Recovery of Ammonia
Ammonia gas is recovered from the remaining solution by treating it with Calsium Hydroxide.
2NH4Cl + Ca(OH)2 ----> CaCl2 + 2H2O + NH3
XII Chemistry BIEK Topic - Chlorine (Castner-Kellner's)
Chlorine (Castner-Kellner's)
Introduction
Chlorine plays an important role in industries. Therefore to fulfill the demands, chlorine is manufactured on large scale. It is prepared by the electrolysis of aqueous solution sodium chloride, this process is known as Castner-Kellner's Process and it is carried out in Castner-Kellner's Cell.
Construction of Castner-Kellner's Cell
The Castner-Kellner's cell consist of a steel tank which contain Hg flows from right to left in the cell and is connected with the negative terminal of the battery therefore it acts as cathode. The cell is filled with saturated aqueous solution of NaCl, which also flows in the same direction as Hg. Some graphite rods are dipped into the solution of NaCl. These rods connected with positive terminal of the battery therefore act as anode.
Working Of Castner-Kellner's Cell
When the electric current is passed through the cell. The sodium ion and chloride ion migrates towards their respective electrodes. Chlorine ion moves towards anode, loses its electron and converts into chlorine gas. The free chlorine gas comes out of the tube at the top of the cell. The sodium ion migrates towards cathode gains electrons and converts into sodium metal. The sodium is dissolved in Hg to form sodium amalgum which comes out with the flow of Hg from the cell.
NaCl <----> Na+ + Cl-
Na+ + e- ----> Na0 (At Cathode)
2Cl ----> Cl2↑ + 2e (At anode)
Introduction
Chlorine plays an important role in industries. Therefore to fulfill the demands, chlorine is manufactured on large scale. It is prepared by the electrolysis of aqueous solution sodium chloride, this process is known as Castner-Kellner's Process and it is carried out in Castner-Kellner's Cell.
Construction of Castner-Kellner's Cell
The Castner-Kellner's cell consist of a steel tank which contain Hg flows from right to left in the cell and is connected with the negative terminal of the battery therefore it acts as cathode. The cell is filled with saturated aqueous solution of NaCl, which also flows in the same direction as Hg. Some graphite rods are dipped into the solution of NaCl. These rods connected with positive terminal of the battery therefore act as anode.
Working Of Castner-Kellner's Cell
When the electric current is passed through the cell. The sodium ion and chloride ion migrates towards their respective electrodes. Chlorine ion moves towards anode, loses its electron and converts into chlorine gas. The free chlorine gas comes out of the tube at the top of the cell. The sodium ion migrates towards cathode gains electrons and converts into sodium metal. The sodium is dissolved in Hg to form sodium amalgum which comes out with the flow of Hg from the cell.
NaCl <----> Na+ + Cl-
Na+ + e- ----> Na0 (At Cathode)
2Cl ----> Cl2↑ + 2e (At anode)
XII Chemistry BIEK Topic - Nitric Acid (Ostwald's Process)
Nitric Acid (Ostwald's Process)
Introduction
On industrial process three methods are employed for the manufacture of nitric acid. Ostwald's Process uses Ammonia as raw material.
Ostwald's Process
When a mixture of ammonia and air is passed through a catalytic chamber containing electrically heated Platinum Gauze, (NO) nitric oxide is formed. This nitric oxide combines with more oxygen to form nitrogen dioxide (NO2). This gas is then absorbed by water to form nitric acid. The plant used in Ostwald's Process consist of following parts.
1. Catalytic Chamber
A mixture of pure and dry ammonia is passed through a catalytic chamber containing heated (800ºC) platinum, which serves as catalyst. Here ammonia is completely oxidized to nitric oxide.
2. Oxidation Tower
The nitric oxide is passed into oxidation tower where the temperature of gases falls to 200ºC - 250ºC. At this temperature nitric is oxidized to nitrogen dioxide.
2NO + O2 ----> 2NO2
3. Absorption Tower
Now the gases containing NO2 and oxygen are than sent to a series of absorption tower, which is filled with broken quartz and water is showered from top of the tower. Then NO2 reacts with H2O in the presence of oxygen to form HNO3.
4NO2 + 2H2O + O2 ----> $HNO3
Introduction
On industrial process three methods are employed for the manufacture of nitric acid. Ostwald's Process uses Ammonia as raw material.
Ostwald's Process
When a mixture of ammonia and air is passed through a catalytic chamber containing electrically heated Platinum Gauze, (NO) nitric oxide is formed. This nitric oxide combines with more oxygen to form nitrogen dioxide (NO2). This gas is then absorbed by water to form nitric acid. The plant used in Ostwald's Process consist of following parts.
1. Catalytic Chamber
A mixture of pure and dry ammonia is passed through a catalytic chamber containing heated (800ºC) platinum, which serves as catalyst. Here ammonia is completely oxidized to nitric oxide.
2. Oxidation Tower
The nitric oxide is passed into oxidation tower where the temperature of gases falls to 200ºC - 250ºC. At this temperature nitric is oxidized to nitrogen dioxide.
2NO + O2 ----> 2NO2
3. Absorption Tower
Now the gases containing NO2 and oxygen are than sent to a series of absorption tower, which is filled with broken quartz and water is showered from top of the tower. Then NO2 reacts with H2O in the presence of oxygen to form HNO3.
4NO2 + 2H2O + O2 ----> $HNO3
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