Electrolysis
Why does the chlorine gas contain a small amount of oxygen?
This is because very few OH- are also discharged producing these oxygen gases.
State Three Uses of Chlorine
PVC, CFCs, Table Salt, Bleach and Disinfectant, Antiseptics, Solvent, Pesticides, Insecticide
What is the most concern pollutant from the Chlor-alkali industry?
Mercury
Why aren't Graphite electrodes used?
Graphite electrodes shorten the lifespan of the diaphragm by plugging it with particles of graphite.
State three uses of PVC
Piping, electrical insulation, bags, clothing and upholstery
What poisoning disease is caused from the chlor-alkali industry?
Methylmercury
What are the ions discharged at each electrode by equations?
Anode: 2Cl-(aq)--> Cl2(g) + 2e-
4OH-(aq) → 2H2O(l) + O2(g) + 4e-
Cathode: 2H+(aq)+ 2e- → H2 (g)
Why is chlorine used broadly in bleach and disinfectant?
This is because chlorine has a very strong oxidizing action.
State three advantages of chlorine production.
Low energy requirements
Operates at a low voltage
Brine can be low purity
Abundant and cheap materials
Asbestos is chemically stable, relatively inexpensive and abundant
Very cost effective
Chlorine chemistry used in bleaches and disinfectant can provide low-cost products for consumers.
How is NaCl is recycled in electrolysis?
NaOH contaminated with NaCl is drained from the anode compartment as well. On partial evaporation the NaCl is crystallized out of the NaOH and recycled to make more brine.
Why is Chlorine used in the manufacture of antiseptics?
This is because it kills the pathogens such as bacteria by breaking the chemical bonds in their molecules.
Discuss TWO environmental concerns associated with the production of chlorine using the diaphragm cell
Asbestos used in the diaphragm cell releases asbestos fibers in the air and can cause lung cancer.
Sodium hydroxide can leak into the environment, alter the pH of water and as a result, lead to the death of organisms.
What is the reason for the ion being charged at the anode and what is the electrode made of?
The Cl- ions have a higher concentration than the OH- ions. Usually OH- ions are preferentially discharged over Cl- however in this case concentration wins over ease of discharge.
As such Chlorine ions are discharged as they oxidize to produce chlorine gas:
2Cl-(aq) → Cl2(g) + 2e-
Why is PVC so used in the construction industry?
Its extremely durable nature and inability to rust or decompose.
How does CFCs contribute to the degradation of the ozone layer?
Light breaks down CFCs, releasing highly reactive chlorine atoms. These initiate a chain reaction that converts ozone to oxygen.