• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Extraction of Halogens: Iodine and Chlorine.

Extracts from this document...

Introduction

Extraction of Halogens: Iodine and Chlorine A method of extracting chlorine is via the membrane cell. This process is described below: On one side circulating brine is in contact with a titanium anode and chloride ions are discharged producing chlorine gas: 2Na+ (aq) + 2Cl-(aq) 2Na+ (aq) + Cl2 (g) + 2e- A steel cathode supplies electrons to the water to liberate hydrogen gas and hydroxide ions: 2Na+ (aq) + 2H2O (l) + 2e- 2Na+ (aq) + H2 (g) + 2OH-(aq) Any chemical reaction which involves oxidation and reduction is described as a redox reaction. This therefore causes the above reactions to also be described at redox reactions as reduction and oxidation are taking place. [3] In the process of extraction of halogens it is necessary to keep apart the products formed at both the cathode and anode in order to prevent them reacting. A mercury cathode cell can be used to achieve this, as the products are produced in different containers. Electrolysis takes place in the first container; this contains anodes coated with a metal oxide; Chlorine ions are discharged here. ...read more.

Middle

This method of burning kelp lasted until 1930. Extraction of iodine from brine and nitrate ores has become the two major sources of the element most recently. Both of these extractions occur due to redox reactions and can be shown by the following reactions: Step One. Brine is reacted with chlorine: 2I- (aq) + Cl2 (g) I2 (aq) + 2Cl- (aq) Step Two. Sulphur dioxide is added to reduce vaporised iodine: SO2 (g) + I2 (aq) + H2O (l) 2H+ (aq) + 2I- (aq) + H2SO4 (aq) Step one is now repeated to form a higher concentration of iodine than its solubility, so that iodine crystals separate and can be recovered by filtration. From Nitrate ores, iodine is formed from iodate (V) ions IO3- (Sodium iodate (V)). During this method, sodium nitrate ore is leached with water which results in the sodium nitrate to crystallise when cooling. After these crystals are separated, a spray of this solution I passed into sulphur dioxide with reduces the iodate (V) ions. IO3- (aq) ...read more.

Conclusion

This therefore would cause the iodine to be contaminated and extremely dilute. * In connection with the nitrate ore, if electrodes were used to extract iodine, nitrate would also be formed alone with iodine. It is evident from the following diagram that as nitrate is a negatively charged ion it would also be discharged at the anode. This therefore results in the present methods of extracting iodine to be used as it allows a high concentration of uncontaminated iodine to be formed. Each of the processes used for both halogens are extremely efficient. Membrane cell used for nitrate ore Substance Annual mass used in the world Percentage Applications Chlorine 39 million tonnes 27% 17% 16% 13% 6% 21% chloroenthane, chloromethanes, solvents (e.g. CHCl=CCl2), inorganixs (e.g. HCl,NaClO), propene oxide, miscellaneous compounds (e.g. water purification, insecticides). Iodine [1] 13 000 tonnes 25% 15% 15% 15% 10% 20% pharmaceutical products, used as catalysts, an ingredient of printing inks and dyes, animal feedstuffs, photographic chemicals, miscellaneous compounds. Hydrogen 36 million tonnes 53% 20% 7% 20% ammonia, oil refinery processes, methanol, other processes. Sodium hydroxide 41 million tonne 30% 16% 5% 5% 5% 5% 34% manufacture of chemicals (e.g. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Changing Materials - The Earth and its Atmosphere section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Changing Materials - The Earth and its Atmosphere essays

  1. Peer reviewed

    What is a metal ore?

    4 star(s)

    Cu, Al pure metals in the form of wires are used for carrying electrical currents. This is used everywhere in industries as well as in homes. 2. Fe, Al, Cu metals are used to make utensils used for cooking. These are also used to make useful equipments for factories. 3.

  2. Chemical Reactions in the Kitchen

    It is said that we are to eat an average of 4-5 eggs every week. This will maintain our cholesterol and fiber. However, if we eat too much eggs or very little, then it will affect the cholesterol in our body by either having low cholesterol because of very little

  1. Plastics- A Benefit or a Disaster? (Science research coursework)

    According to a 2001Environment Agency report, 80% of post-consumer plastic waste is sent to landfill, 8% is incinerated and only 7% is recycled. Disposing of waste in a landfill involves burying the waste. A properly-designed and well-managed landfill can be a hygienic and relatively inexpensive method of disposing of waste materials.

  2. Investigating how the amount of copper affects the mass of the cathode

    solution may loose or gain electrons and are changed into neutral atoms. The reaction at the electrode depends on the voltage that is applied. Here is an example of what I expect to happen in this experiment. When the solution of copper sulphate has dissolved in water, it divides into positive copper ions and negative sulphate ions.

  1. Making an electric cell

    Understanding the ideas behind a reference electrode Suppose you had an optical device for measuring heights some distance away, and wanted to use it to find out how tall a particular person was. Unfortunately, you can't see their feet because they are standing in long grass.

  2. Life's Essential Elements: Chlorine & Iodine.

    ions stay in the anode compartment. Here chloride ions in the circulating brine come into contact with the titanium anode coated with an electrocatalytic layer of mixed oxides^ (1) and are oxidized resulting in the production of chlorine gas. [image007.gif] 2Na^+(aq) + 2 Cl^-(aq) 2Na^+(aq)+ Cl[2](g)

  1. Extraction of chlorine and iodine

    About 0.25% to 0.5% sodium amalgam is produced in the cell. The sodium amalgam reacts with water in the decomposer (the second container), packed with graphite particles and produces caustic soda and hydrogen. Hydrogen, saturated with water vapours, exits from the top along with the mercury vapours.

  2. Describe the reactions which take place at the electrodes in the membrane cell and ...

    This is because the products are produced in different halves of the membrane cell. As certain ions can't pass through the membrane, the products are successfully separated with no mixing or harmful substances used. This means it doesn't need a large electrical supply to force products apart.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work