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3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||99.424 g/mol|
|Density||3.053 g/cm3, solid|
|Melting point||125 °C (257 °F; 398 K) (decomposition)|
Solubility in water
Solubility product (Ksp)
|Solubility in alcohol||insoluble|
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Magnetic susceptibility (χ)
Std enthalpy of
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Zinc hydroxide Zn(OH)2 is an inorganic chemical compound. It also occurs naturally as 3 rare minerals: wülfingite (orthorhombic), ashoverite and sweetite (both tetragonal).
Like the hydroxides of other metals, such as lead, aluminium, beryllium, tin cậy and chromium, Zinc hydroxide (and Zinc oxide), is amphoteric. Thus it will dissolve readily in a dilute solution of a strong acid, such as HCl, and also in a solution of an alkali such as sodium hydroxide.
It can be prepared by adding sodium hydroxide solution, but not in excess, đồ sộ a solution of any zinc salt. A white precipitate will be seen:
- Zn2+ + 2 OH− → Zn(OH)2.
Zn2+ is known đồ sộ khuông hexa-aqua ions at high water concentrations and tetra-aqua ions at low concentrations of water  and, thus, this reaction may be better written as the reaction of the aquated ion with hydroxide through donation of a proton, as follows.
- Zn2+(OH2)4(aq) + OH−(aq) → Zn2+(OH2)3OH−(aq) + H2O(l)
Subsequent reactions discussed below can also, therefore, be considered as reactions with the aquated zinc ion and one can adjust them accordingly. However, for simplicity, the water molecules are omitted from here-on.
If excess sodium hydroxide is added, the precipitate of zinc hydroxide will dissolve, forming a colorless solution of zincate ion:
- Zn(OH)2 + 2 OH− → Zn(OH)42−.
This property can be used as a test for zinc ions in solution, but it is not exclusive, since aluminium and lead compounds behave in a very similar manner. Unlike the hydroxides of aluminium and lead, zinc hydroxide also dissolves in excess aqueous ammonia đồ sộ khuông a colorless, water-soluble ammine complex.
Zinc hydroxide will dissolve because the ion is normally surrounded by water ligands; when excess sodium hydroxide is added đồ sộ the solution the hydroxide ions will reduce the complex đồ sộ a −2 charge and make it soluble. When excess ammonia is added, it sets up an equilibrium which provides hydroxide ions; the formation of hydroxide ions causes a similar reaction as sodium hydroxide and creates a +2 charged complex with a co-ordination number of 4 with the ammonia ligands - this makes the complex soluble so sánh that it dissolves.
One major use is as an absorbent in surgical dressings. It is also used đồ sộ find zinc salts by mixing sodium hydroxide with the suspect salt.
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- ^ Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN 0-618-94690-X.
- ^ Sze, Yu-Keung, and Donald E. Irish. "Vibrational spectral studies of ion-ion and ion-solvent interactions. I. Zinc nitrate in water." Journal of Solution Chemistry 7.6 (1978): 395-415.
- Chemistry in Context - By Graham Hill, John Holman (pp. 283,284)