Silver chloride
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| Silver chloride | |
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Silver(I) chloride |
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Other names
cerargyrite |
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| Identifiers | |
| CAS number | 7783-90-6  |
| PubChem | 24561 |
| ChemSpider | 22967 |
| UNII | MWB0804EO7 |
| ChEBI | CHEBI:30341 |
| RTECS number | VW3563000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | AgCl |
| Molar mass | 143.32 g mol−1 |
| Appearance | White Solid |
| Density | 5.56 g cm−3 |
| Melting point |
455 °C, 728 K, 851 °F |
| Boiling point |
1547 °C, 1820 K, 2817 °F |
| Solubility in water | 520 μg/100 g at 50 °C |
| Solubility | insoluble in alcohol, dilute acid soluble in ammonia, concentrated sulfuric acid, alkali cyanide, NH4CO3, KBr, sodium thiosulfate |
| Refractive index (nD) | 2.071 |
| Structure | |
| Crystal structure | halite |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
−127 kJ·mol−1[1] |
| Standard molar entropy S |
96 J·mol−1·K−1[1] |
| Hazards | |
| MSDS | Salt Lake Metals |
| NFPA 704 |
 0
2
0
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| Related compounds | |
| Other anions | silver(I) fluoride, silver bromide, silver iodide |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Silver chloride is a chemical compound with the chemical formula Ag1+Cl1-. This white crystalline solid is well known for its low solubility in water (this behavior being reminiscent of the chlorides of Tl+ and Pb2+). Upon illumination or heating, silver chloride converts to silver (and chlorine), which is signalled by greyish or purplish coloration to some samples. AgCl occurs naturally as a mineral chlorargyrite.
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[edit] Preparation
Silver chloride is easily synthesized by combining aqueous solutions of silver nitrate and sodium chloride.
- AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)
[edit] Structure and reactions
The solid adopts the fcc NaCl structure, in which each Ag+ ion is surrounded by an octahedron of six chloride ligands. AgF and AgBr crystallize similarly.[2] However, the crystallography depends on the condition of crystallization, primarily free silver ion concentration, as is shown on the pictures left (greyish tint and metallic lustre are due to partly reduced silver). AgCl dissolves in solutions containing ligands such as chloride, cyanide, triphenylphosphine, thiosulfate, thiocyanate and ammonia. Silver chloride reacts with these ligands according to the following illustrative equations:
- AgCl(s) + Cl−(aq) → AgCl2−(aq)
- AgCl(s) + 2S2O32−(aq) → [Ag(S2O3)2]3−(aq) + Cl−(aq)
- AgCl(s) + 2NH3(aq) → [Ag(NH3)2]+(aq) + Cl−(aq)
Most complexes derived from AgCl are two-, three-, and, in rare cases, four-coordinate, adopting linear, trigonal planar, and tetrahedral coordination geometries, respectively.
[edit] Chemistry
In one of the most famous reactions in chemistry, addition of colorless aqueous silver nitrate to an equally colorless solution of sodium chloride produces an opaque white precipitate of AgCl:[3]
This conversion is a common test for the presence of chloride in solution. Due to its conspicuousness it is easily used in titration, which gives the typical case of argentometry.
The solubility product, Ksp, for AgCl is 1.6 x 10−10, which indicates that one liter of water will dissolve 0.000013 moles (1.9 mg) of AgCl at room temperature. The chloride content of an aqueous solution can be determined quantitatively by weighing the precipitated AgCl, which conveniently is non-hygroscopic, since AgCl is one of the few transition metal chlorides that is unreactive toward water. Ions that interfere with this test are bromide and iodide, as well as a variety of ligands (see silver halide). For AgBr and AgI, the Ksp values are 5.2 x 10−13 and 8.3 x 10−17, respectively. The silver bromide (slightly yellowish white) and silver iodide (pale yellow) are also significantly more photosensitive than is AgCl.
AgCl quickly darkens on exposure to light by disintegrating into elemental chlorine and metallic silver. This reaction is used in photography and film.
[edit] Uses
- Silver chloride is used to make photographic paper since it reacts with photons to form latent image and via photoreduction.
- The silver chloride electrode is a common reference electrode in electrochemistry.
- Silver chloride's low solubility makes it a useful addition to pottery glazes for the production of "Inglaze lustre".
- Silver chloride has been used as an antidote for mercury poisoning, assisting in the elimination of mercury.
- Silver chloride is often used in photochromic lenses, again taking advantage of its reversible conversion to Ag metal.
- Silver chloride is used to create yellow, amber, and brown shades in stained glass manufacture.
- Silver chloride is used in bandages and wound healing products.
- Silver chloride is used as an antimicrobial agent in some personal deodorant products.
- Silver chloride is used as an antimicrobial agent for long-term preservation of drinking water in water tanks.
[edit] References
- ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed.. Houghton Mifflin Company. p. A23. ISBN 061894690X.
- ^ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
- ^ More info on Chlorine test
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