Strontium Chloride: Formula, Chemical Structure, Uses, Preparation and Properties

He strontium chloride is an inorganic compound formed by strontium, alkaline earth metal (Mr. Becamgbara) and halogen chlorine. Because both elements have very different electronegativities, the compound is an ionic solid whose chemical formula is SrCl 2 .

As it is an ionic solid, it is constituted by ions. For the case of SrCl 2 , they are a cation Sr 2+ for every two Cl anions - . Its properties and applications are similar to calcium and barium chlorides, with the difference that strontium compounds are relatively rare to obtain and, therefore, more expensive.

Like calcium chloride (CaCl 2 ), it is hygroscopic and its crystals absorb water to form the hexahydrated salt, in which six water molecules are present in the crystalline lattice (SrCl 2 · 6H 2 Or, superior image). In fact, commercially, the availability of hydrate is greater than that of SrCl 2 anhydrous (without water).

One of its main applications is as a precursor of other strontium compounds; that is, it constitutes the source of strontium in certain chemical syntheses.

Index

  • 1 Chemical structure
  • 2 Applications
    • 2.1 Medicinal
  • 3 Preparation
  • 4 Properties
    • 4.1 Anhydrous
    • 4.2 Hexahydrate
  • 5 References

Chemical structure

The upper image represents the deformed rutile crystal structure of SrCl 2 anhydrous. In this, the small green spheres correspond to the ions Sr 2+ , while bulky green spheres represent Cl ions - .

In this structure each ion Sr 2+ is"imprisoned"by eight Cl ions - , consequently having a coordination number equal to 8 and, possibly, a cubic geometry around it. That is, four green spheres make up the roof of the cube, while the other four spheres make up the floor of the cube, while 2+ in the center of it.

What would be the gas phase structure? The Lewis structure for this salt is Cl-Sr-Cl, apparently linear and assuming a covalence of one hundred percent of its bonds. However, in the gaseous phase â €"SrCl 2 (g) - this"line"shows an angle of approximately 130º, being actually a kind of V.

This anomaly could not be explained successfully, considering the fact that strontium does not have non-shared electrons that occupy electronic volume. Perhaps it can be caused by the participation of an orbital d in the bonds, or a nucleus-electron perturbation.

Applications

The SrCl 2 · 6H 2 Or it has been used as an additive in organic polymers; for example, in polyvinyl alcohol, in order to modify its mechanical and electrical properties.

It is used as strontium ferrite in the manufacture of ceramic magnets and glass destined to make the color front glass of television.

Reacts with sodium chromate (Na 2 CrO4) to produce strontium chromate (SrCrO 4 ), which is used as a corrosion resistant paint for aluminum.

When heated with fire, the strontium compounds shine with a reddish flame, which is why they are destined to the elaboration of flares and fireworks.

Medicinal

The radioisotope of strontium chloride 89 (the most abundant isotope is 85 Sr) is used in the field of medicine to reduce bone metastases by selectively injecting intravenously into the bone tissue.

The use of diluted solutions (3-5%) for more than two weeks in the treatment of allergic rhinitis (chronic inflammation of the nasal mucosa), shows improvements in the reduction of sneezing and nasal rub.

It was once used in toothpaste formulations to reduce tooth sensitivity, forming a barrier over dentinal microtubules.

Studies of this compound demonstrate a therapeutic efficacy compared to prednisolone (metabolite of the drug prednisone) in the treatment of ulcerative colitis.

Their results are based on the model of the organism of the rats; even so it represents a hope for those patients who also suffer from osteoporosis, since they can go to the same medicine to fight the two diseases.

It is used to synthesize strontium sulfate (SrSO) 4 ), even more dense than SrCl 2 . However, its minimal solubility in water does not make it light enough to be applied in radiology, unlike barium sulfate (BaSOl). 4 ).

Preparation

Strontium chloride can be prepared by direct action of hydrochloric acid (HCl) on the pure metal, thus producing a redox type reaction:

Sr (s) + HCl (ac) => SrCl 2 (ac) + H 2 (g)

Here, the strontium metal is oxidized by donating two electrons to allow the formation of gaseous hydrogen.

Also, hydroxide and strontium carbonate (Sr (OH) 2 and SrCO 3 ) react with this acid when synthesizing it:

Sr (OH) 2 (s) + 2HCl (ac) => SrCl 2 (ac) + 2H 2 O (l)

SrCO 3 (s) + 2HCl (ac) => SrCl 2 (ac) + CO 2 (g) + H 2 O (l)

Applying crystallization techniques, SrCl is obtained 2 · 6H 2 O. Then it is dehydrated by thermal action until finally producing SrCl 2 anhydrous.

Properties

The physical and chemical properties of this compound depend on whether it is in its hydrated or anhydrous form. This is due to the fact that the electrostatic interactions change as the water molecules are added to the crystalline lattice of the SrCl 2 .

Anhydrous

Strontium chloride is a white crystalline solid, with a molecular weight of 158.53 g / mol, and a density of 3.05 g / mL.

Its melting point (874 ° C) and boiling point (1250 ° C) are high, indicative of strong electrostatic interactions between Sr ions 2+ and Cl - . Likewise, it reflects the great crystalline reticular energy that its anhydrous structure possesses.

The enthalpy of formation of SrCl 2 solid is 828.85 KJ / mol. This refers to the thermal energy released by each mol formed from its components in its standard states: gas for chlorine and solid for strontium.

Hexahydrate

In the form of hexahydrate it has a molecular weight higher than its anhydrous form (267 g / mol), and a lower density (1.96 g / mL). This decrease in density is due to water molecules"dilate"the crystals, increasing the volume; therefore, the density of the structure decreases.

It is almost twice as dense as water at room temperature. Its solubility in water is very high, but in ethanol it is slightly soluble. This is due to its organic character despite its polarity. That is, the hexahydrate is a polar inorganic compound. Finally, at 150 ° C, it is dehydrated to produce the anhydrous salt:

SrCl 2 · 6H 2 O (s) => SrCl 2 (s) + 6H 2 O (g)

References

  1. Wikipedia. (2018). Strontium chloride. Retrieved on April 13, 2018, from: en.wikipedia.org
  2. DrugBank. (2018). Strontium chloride Sr-89. Retrieved on April 13, 2018, from: drugbank.ca
  3. Pubchem. (2018). Strontium Chloride. Retrieved on April 13, 2018, from: pubchem.ncbi.nlm.nih.gov
  4. Altuntas, E. E., Turgut, N. H., Durmuş, K., Doğan, Ö. T., & Akyol, M. (2017). Strontium chloride hexahydrate as a candidate molecule for long-term treatment of allergic rhinitis. The Indian Journal of Medical Research , 146 (1), 121-125. doi.org
  5. Firdevs Topal, Ozlem Yonem, Nevin Tuzcu, Mehmet Tuzcu, Hilmi Ataseven, and Melih Akyol. (2014). Strontium Chloride: Can It Be a New Treatment Option for Ulcerative Colitis? BioMed Research International, vol. 2014, Article ID 530687, 5 pages. doi: 10.1155 / 2014/530687
  6. Bull. Mater. (2010). Influence of granular strontium chloride as additives on some electrical and mechanical properties for pure polyvinyl alcohol. Sci., Vol. 33, No. 2, pp. 149-155. Indian Academy of Sciences.
  7. Maria Perno Goldie, RDH, MS. (March 15, 2011). Potassium nitrate, sodium fluoride, strontium chloride, and NovaMin technologies for dentin hypersensitivity. Retrieved on April 13, 2018, from: dentistryiq.com
  8. CCoil. (September 4, 2009). Strontium-chloride-xtal-3D-SF. [Figure]. Retrieved on April 13, 2018, from: commons.wikimedia.org
  9. All reactions. SrCl2 - Strontium Chloride. Retrieved on April 13, 2018, from: allreactions.com


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