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From Wikipedia

Magnesium chloride

Magnesium chloride is the name for the chemical compounds with the formulas MgCl2 and its various hydrates MgCl2(H2O)x. These salts are typical ionic halides, being highly soluble in water. The hydrated magnesium chloride can be extracted from brine or sea water. Magnesium chloride as the natural mineral bischofite is also extracted (solution mining) out of ancient seabeds, for example the Zechstein seabed in northwest Europe. Anhydrous magnesium chloride is the principal precursor to magnesium metal, which is produced on a large scale.

Structure, preparation, and general properties

MgCl2 crystallizes in the cadmium chloride motif, which features octahedral Mg. A variety of hydrates are known with the formula MgCl2(H2O)x, and each loses water with increasing temperature: x = 12 (-16.4 °C), 8 (-3.4 °C), 6 (116.7 °C), 4 (181 °C), 2 (ca. 300 °C). In the hexahydrate, the Mg2+ remains octahedral, but is coordinated to six water ligands. The thermal dehydration of the hydrates MgCl2(H2O)x (x = 6, 12) does not occur straightforwardly.

As suggested by the existence of some hydrates, anhydrous MgCl2 is a Lewis acid, although a relatively weak one.

In the Dow process, magnesium chloride is regenerated from magnesium hydroxide using hydrochloric acid:

Mg(OH)2(s) + 2 HCl → MgCl2(aq) + 2 H2O(l)

It can also be prepared from magnesium carbonate by a similar reaction.

In most of its derivatives, MgCl2 forms octahedral complexes. Derivatives with tetrahedral Mg2+ are less common. Examples include salts of (tetraethylammonium)2MgCl4 and adducts such as MgCl2(TMEDA).

Applications

Magnesium chloride serves as precursor to other magnesium compounds, for example by precipitation:

MgCl2(aq) + Ca(OH)2(aq) → Mg(OH)2(s) + CaCl2(aq)

It can be electrolysed to give magnesium metal:

MgCl2(l) → Mg(l) + Cl2(g)

This process is practiced on a substantial scale.

Magnesium chloride is used for a variety of other applications besides the production of magnesium: the manufacture of textiles, paper, fireproofing agents, cements and refrigeration brine, and dust and erosion control. Mixed with hydrated magnesium oxide, magnesium chloride forms a hard material called Sorel cement.

Magnesium ion Mg2+ (usually added as the chloride) is an important component in the polymerase chain reaction, a procedure used to amplify DNA fragments. It is generally used in experimental biology whenever RNA and DNA and their enzymes are to function in vitro, since Mg2+ is a necessary associate ion for nucleotides in biology, such as ATP.

Magnesium chloride is also used in several medical and topical (skin related) applications. It has been used in pills as supplemental sources of magnesium, where it serves as a soluble compound which is not as laxitive as magnesium sulfate, and more bioavailable than magnesium hydroxide and magnesium oxide, since it does not require stomach acid to produce soluble Mg2+ ion. It can also be used as an effective anaesthetic for cephalopods, some species of crustaceans, and several species of bivalve, including oysters.

Culinary use

Magnesium chloride is an important coagulant (E511 ) used in the preparation of tofu from soy milk. In Japan it is sold as nigari (��り, derived from the Japanese word for "bitter"), a white powder produced from seawater after the sodium chloride has been removed, and the water evaporated. In China it is called lushui (�水). Nigari or lushui consists mostly of magnesium chloride, with some magnesium sulfate and other trace elements. It is also an ingredient in baby formula milk.

Use as

Aqueous solution

An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending (aq) to the relevant formula. The word aqueous means pertaining to, related to, similar to, or dissolved in water. As water is an excellent solvent and is also naturally abundant, it is an ubiquitous solvent in chemistry.

Substances which are hydrophobic('water fearing') often do not dissolve well in water whereas those thathydrophilic('water-loving') do. An example of a hydrophilic substance would besodium chloride (ordinary table salt). Acids and bases are aqueous solutions, as part of their Arrhenius definitions.

The ability of a substance to dissolve in water is determined by whether the substance can match or exceed the strong attractive forces that water molecules generate between themselves. If the substance lacks the ability to dissolve in water the molecules form a precipitate.

Aqueous solutions that conduct electric current efficiently contain strong electrolytes, while ones that conduct poorly are considered to have weak electrolytes. Those strong electrolytes are substances that are completely ionized in water, whereas the weak electrolytes exhibit only a small degree of ionization in water.

Nonelectrolytes are substances that dissolve in water, but which maintain their molecular integrity (do not dissociate into ions). Examples include sugar, urea, glycerol, and methylsulfonylmethane (MSM).

When performing calculations regarding the reacting of one or more aqueous solutions, one generally must know the concentration, or molarity, of the aqueous solutions. Solution concentration is given in terms of the form of the solute prior to it dissolving.



From Yahoo Answers

Question:

Answers:You get the gasses hydrogen and chlorine so he process also trys to reduce sodium but this only results in the production of NaOH as sodium reacts with water, so the pH goes up http://en.wikipedia.org/wiki/Chlorine

Question:What are the products of electrolysis of the following substances (all dissolved in water; please give what electrode they are formed at and their state of matter): Lead nitrate Sulphuric acid Copper sulphate Sodium chloride.

Answers:I usually give students two 'rules' to use in aqueous electrolysis with inert electrodes Cathode - hydrogen gas froms from H+ ions in the water unless ions of a very unreactive metal are present (Cu, Ag, Au) in which case the unreactive metal forms Anode - oxygen gas forms from OH- ions in the water unless halide ions (Cl-, Br-, I- ) are present, then the halogen forms so for Pb(NO3)2 you will get hydrogen gas at the cathode and oxygen gas at the anode for H2SO4 you will get hydrogen gas at the cathode and oxygen gas at the anode for CuSO4 you will get copper metal solid at the cathode and oxygen gas at the anode for NaCl you will get hydrogen gas at the cathode and chlorine gas at the anode. Hope this helps.

Question:K here is what i did 9v battery salt water , plastic tub 2 stainless steel bolts hooked the bolts to the battery , and set them in water for about an hour ... started making green water , how deadly was that gas that was produced ?

Answers:"deadly" may be an overstatement... the limited amount of Cl2 gas produced would dissolve in the atmosphere quickly and dissipate without any hazardous effect generally, though concentrated amounts would be harmful if directly inhaled. the bolts may have been chrome plated rather than stainless though as hinted by the "green water" read up on the demo you did a nice job of at the site below

Question:how is chlorine and sodium hydroxide made in the electrolysis of brine? and could you also explain and maybe include some pictures?? and how do industrial processes use these products? and one last thing, any interesting facts about hydrogen, chlorine and sodium hydroxide would be really great!!! i love chemistry :) i wana be a biomedical scientist wen im older so i have to get all A*s lol thankss :)

Answers:Brine is the industrial name for a strong solution of Sodium chloride. Sodium chloride is table salt - the stuff that you put on your food. The formula for table salt - sodium chloride is NaCl. When NaCl is dissolved in water, its separates into its ions. NaCl(s) = Na^+(aq) + Cl^-(aq) The sodium ion has lost one electron so it has a positive (+) charge, The Chloride ion has gained one electron so it has a negative(-) charge. Two electrodes are placed in the solution and an electric current is passed through. The Cathode is electron rich and the Anode is electron poor. So the sodium cation (Na^+), since it is short of one electron, will migrate towards the electron rich cathode, 'pick up' an electron and becomes sodium metal. Conversely, the chloride anion (Cl^-), since it has one extra electron, will migrate towards the electron poor anode, and deposit its extra electron on to the anode, and becomes chlorine gas. Hence chlorine is liberated at the Anode. Chlorine is a green coloured gas. However, when sodium metal is formed at the Cathode, because it is in aqueous solution, immediately reacts with the water, to form Sodium hydroxide and hydrogen. Hence hydrogen is liberated at the cathode, and the brine solution becomes more alkaline as the hydroxide is formed. 2Na + 2H2O = 2NaOH(aq) + H2(g) Industrial processes Hydrogen - Hydrogenation of oils and fats to make margarine. Chlorine - Bleaching Sodium hydroxide - soap making Interesting Facts. Hydrogen - the lighest element - inflammable. Chlorine - Green coloured gas - pugent and poisonous. Sodium hydroxide - Also called Caustic Soda - oily transparent liquid.- corrosive.

From Youtube

Electrolysis Of Sodium Chloride :doing electrolysis on the mains electricity after passing it through a transformer, i used pencil 'lead' for the carbon (graphite) electrodes instead of the copper wires so the electrodes themselves wun react. the electrolyte is aqueous sodium chloride (table salt dissolved in water). thanks for the comments, my conclusion: chlorine gas evolved in the test tube... but its yellowish green is light, almost unnoticeable... firstly hydrogen gas will form at the cathode as sodium is too reactive to be extracted there. its electrolysis of aqueous sodium chloride not molten one anyway... chlorine gas will be formed at the anode as i put in plenty of salt in the water

Electrolysis sodium chloride to Sodium hypochlorite :Improvised Electrolysis of sodium chloride to sodium gypochlorite (when higher temp, there can be sodium chlorate). Better image of electrolyser there - img262.imageshack.us