Chlor-alkali industry Flashcards
Salts can be extracted from underground deposits by….
Solution mining - Very hot water under high pressure is pumped down into deposits
Salt dissolves & solution is pumped back to surface
What does a diaphragm cell do
Concentrated salt solution is electrolysed in diaphragm cell to produce sodium hydroxide, hydrogen and chlorine
Keep the products apart
Why is it important to keep the products apart
Because if chlorine reacts with sodium hydroxide it produces bleach
If chlorine reacts with hydrogen it explodes violently to produce hydrogen chloride
What is happening at the anode in a diaphragm cell
Chlorine ions are discharged to produce chlorine gas 2Cl- –> Cl2+2e-
What is the anode made of
Titanium
What is the cathode made of in the diaphragm
Steel
What is happening at the cathode in the diaphragm
Too difficult to discharge sodium ions - hydrogen ions from water discharged to give hydrogen gas
2H+ +2E- –> H2
What is fed into the diaphragm cell
Concentrated sodium chloride
Sodium chloride solution is concentrated by
Evaporating, most of the sodium chloride crystals out as a salt. This can be separated redid solved in water and recycled back through the cell
Uses of sodium hydroxide
Purifying bauxite to make aluminium oxide
Paper making, breaks wool down into a pulp
Soap making reacts with fats to make soap
Making bleach sodium hydroxide & chlorine react in the cold
Equation for making bleach
2NaOH + CL2 –> NaCl+NaOCL+H2O
Uses of chlorine
Sterilising water, making hydrochloric acid, making bleach
How does a diaphragm cell produce sodium hydroxide
Water splits up to hydrogen ions, hydroxide ions are also produced
Build up of sodium ions & hydroxide ions in right hand compartment
Sodium hydroxide solution formed
