Sodium Thiosulfate - Structure, Application, Preparation, Uses, FAQs

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The inorganic compound with the chemical formula Na₂S₂O₃.XH₂O is called sodium thiosulfate. XH₂O suggested that it is present in its hydrated form. Generally it is present in its a pentahydrate a form that is the chemical formula is Na₂S₂O₃.5H₂O. It is a white colorless compound and it loses its water easily and dissolves well in water.

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Na2S2O3 structure
Uses of sodium thiosulphate
Chemical reactions of sodium thiosulphate
Preparation of sodium thiosulphate
Hypo solution

The molecular mass of sodium thiosulfate is 158.11 gram per mole when it is present in the anhydrous former and if it is in the hydrated form that is pending hydrated form the value of molecular weight is 248.18 gram per mole. It is a colorless crystal and the density of Na₂S₂O₃ is 1.667 grams per centimeter cube. The melting point of sodium thiosulfate pentahydrate is 321.4k and its boiling point is 100 degrees Celsius.

The solubility in water is high but it is negligible soluble in alcohol. Sodium thiosulfate is prepared by heating sodium sulfite solution with sulfur or by heating sodium hydroxide solution with sulfur. The following equation represents the formation of sodium thiosulphate.

6NaOH+4S→Na₂S₂O₃+2Na₂S+3H₂O

Sodium thiosulphate has also possessed some other names like sodium hyposulphite, and hyposulphite of sodium, hypo, etc.

Sodium thiosulfate crystals

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Sodium thiosulfate has many applications; it is used extensively in gold mining, for the water treatment, for the development of a silver base as a photographic film and prints. One of the important applications of sodium thiosulphate is it can be used as a medicine for cyanide poisoning. In addition to that there are some other medical uses also it is used for the treatment of ringworm and tinea versicolor and also for treating the side effects caused during the chemotherapy treatment.

Thiosulphate has a wide application in the medical field just because it is a non-toxic material. But when sodium thiosulfate is decomposed it will produce sulfur dioxide fumes that are toxic and can cause irritation to skin eyes and even mucous membranes. Thiosulfate is used in analytical chemistry that is in the iodometric titration. Thiosulfate anion reacts with iodine to form iodide the following is the equation for the iodometric titration.

S₂O₃^2-+I₂→S₄O₆^2-+2I^-

In addition to the efficiency in this reaction with iodine thiosulfate also has an excellent shelf life so it is used as a titrant in iodometric titration.

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Na₂S₂O₃ structure

From the chemical formula of sulfur we get to know that it contains two sodium cations and a thiosulphate anion i.e. S₂O₃²^-. The central atom of sulfur forms one bond with the sulfur atom and the other bonded to the remaining oxygen atoms. The central sulfur atom forms a single and double bond in a resonating way. And so the stability of sodium thiosulphate is high. The following figure shows the sodium thiosulfate structure.

Structure of sodium thiosulfate

As shown in the structure, it forms a double bond with one oxygen and a sulfur atom.

Uses of sodium thiosulphate

Due to its low toxicity and highly stable structure, it has a wide range of applications.

Photography

Na₂S₂O₃.5H₂O is used in photography for the reduction of silver to metallic silver. That is for dissolving silver salt from the negatives sodium thiosulfate is used as a fixing agent.

Industrial application

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It is used for the extraction of gold from its ore. And also it is used as a dechlorinating agent for small water bodies like aquariums, ponds, etc. It also has applications in the leather industry that is for the tanning process.

Medical application

For the preparation of pharmaceuticals, sodium thiosulfate is used. The most important application of sodium thiosulfate is used as an antidote for cyanide poisoning. And also it is used for reducing the side effects of chemotherapy.

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Chemical reactions of sodium thiosulphate

The solubility of thiosulfate in water is high and it produces sodium ions and thiosulfate ions. But the compound is insoluble in alcohol.

Na₂S₂O₃+H₂O→Na⁺+S₂O₃^-

The compound is a highly stable compound that we get from the structure itself but when it reacts with dilute acids it is decomposed to produce sulfur. The following equation shows the reaction of sodium thiosulphate with dilute hydrogen chloride acid.

Na₂S₂O₃+2HCl→2NaCl+S+H₂O +SO₂

Although it is a stable compound this decomposes when external heat is supplied to it. The following reaction shows the decomposition of sodium thiosulphate by the application of heat.

4Na₂S₂O₃→3Na₂SO₄+Na₂S₅

Preparation of sodium thiosulphate

Sodium thiosulfate, Na₂S₂O₃ can be prepared by using two methods, one by heating sulfur with sodium sulfite solution. The other method is by boiling sulfur with sodium hydroxide solution. It is generally found in its pentahydrate form and so it is also known as sodium hyposulfite. Sodium thiosulphate is a good reducing agent and so it is used in many reactions.

For iodometric titration sodium thiosulfate is the titrant with the starch as an indicator since starch contains high amounts of iodine. During iodometric titration before iodine forms, a complex with starch sodium thiosulfate reduces iodine to iodide. So it is a very important inorganic salt with very high industrial applications.

Hypo solution

The hypo solution formula is Na₂S₂O₃ and it is also known by the name of sodium thiosulphate solution. Hypo is present in liquid form and the color of the hypo solution is yellowish. Hypo solution is used for the photographic application i.e it is used as a photographic fixer for the development of the image. The hypo solution is used as the dechlorinating agent and also it is used in the iodometric titration as a titrant. It is the compound used for the treatment of cyanide poisoning. Hypochemical name is sodium thiosulfate.

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NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. The equivalent weight of iodine?

127u.

2. Sodium thiosulfate molecular weight?

158.11g/mol.

3. The chemical formula of sodium thiosulphate is ___

Na₂S₂O₃

4. What is Sodium thiosulfate formula?

Na₂S₂O₃

5. What is a hypo solution?

Hypo solution is commonly known by the name of sodium thiosulphate. It is the solution form of sodium thiosulfate that is present in the liquid state. It is a basic compound with many applications in many fields. The chemical formula of hypo solution is similar to sodium thiosulfate that is Na₂S₂O₃. It is used as an intravenous medication for the treatment of poisoning of metals, mainly cyanides. And also used for the treatment of diseases like Calciphylaxis, dermal lesions, etc. It is also used as an anti-calcification and inflammatory agent. It is used as a dechlorinating agent for water bodies like swimming pools, water bodies, etc., and is because of its low toxicity. The name hypo always represents sodium thiosulfate as there are some other compounds like sodium hypochlorite with a similar sound.

6. What is Sodium thiosulfate equivalent weight?

248

7. What is the formula of sodium thiosulphate?

Na₂S₂O₃

8. Write Sodium thiosulfate uses.

It is compound with many industrial as well as medical applications. Below are some of the important uses of sodium thiosulfate. It is used for the treatment of several metals poisoning mainly as an antidote in cyanide poisoning by converting cyanide to a soluble form and thereby removed through the urine.

In the mining of gold sodium thiosulfate is an important component.
It is used as an antifungal medicine on the skin to treat the infections caused by fungus.
For the process of tanning in the leather industry, sodium thiosulfate is used.
As a dechlorinating agent for water bodies like swimming pools, ponds, etc. sodium thiosulfate is used.

9. What is the hypo formula?

Na₂S₂O₃

10. What is Na2S2O3 name?

Sodium thiosulfate.

11. How does sodium thiosulfate behave in aqueous solution?

In aqueous solution, sodium thiosulfate dissociates into sodium ions (Na+) and thiosulfate ions (S2O3^2-). The thiosulfate ion acts as a moderate reducing agent and can participate in various redox reactions.

12. How does sodium thiosulfate react with acids?

When sodium thiosulfate reacts with acids, it decomposes to form sulfur dioxide, water, and elemental sulfur. The reaction can be represented as: Na2S2O3 + 2HCl → 2NaCl + H2O + SO2 + S

13. How does sodium thiosulfate act as an antidote for cyanide poisoning?

Sodium thiosulfate acts as an antidote for cyanide poisoning by providing a sulfur donor. It helps convert toxic cyanide ions into less harmful thiocyanate ions, which can be excreted from the body.

14. What is the significance of the sulfur-sulfur bond in the thiosulfate ion?

The sulfur-sulfur bond in the thiosulfate ion is significant because it contributes to the reducing properties of thiosulfate. This bond can be easily broken, allowing thiosulfate to act as an electron donor in redox reactions.

15. What role does sodium thiosulfate play in analytical chemistry?

In analytical chemistry, sodium thiosulfate is commonly used as a reducing agent in redox titrations. It's particularly useful in iodometry, where it reacts with iodine to form iodide ions and tetrathionate ions.

16. How does the presence of sodium thiosulfate affect the solubility of silver halides?

Sodium thiosulfate increases the solubility of silver halides by forming soluble complex ions. This property is the basis for its use in photography and in dissolving silver chloride precipitates in analytical procedures.

17. How does the presence of sodium thiosulfate affect the pH of a solution?

Sodium thiosulfate is a salt of a strong base (NaOH) and a weak acid (H2S2O3). In aqueous solution, it undergoes hydrolysis to produce a slightly alkaline solution, thus increasing the pH.

18. How does sodium thiosulfate interact with silver bromide in photographic processes?

Sodium thiosulfate forms soluble complex ions with silver bromide in photographic processes. This reaction, represented as AgBr + 2Na2S2O3 → Na3[Ag(S2O3)2] + NaBr, is crucial in fixing photographic images.

19. What is the role of sodium thiosulfate in the textile industry?

In the textile industry, sodium thiosulfate is used as an antichlor agent. It neutralizes excess chlorine after bleaching processes, preventing damage to fabrics and ensuring color fastness.

20. What is the difference between sodium thiosulfate and sodium sulfite?

While both are sulfur-containing sodium salts, sodium thiosulfate (Na2S2O3) contains a sulfur-sulfur bond and has a chain-like structure, whereas sodium sulfite (Na2SO3) has a trigonal pyramidal structure. Thiosulfate is a stronger reducing agent than sulfite.

21. What is the chemical formula of sodium thiosulfate?

The chemical formula of sodium thiosulfate is Na2S2O3. It consists of two sodium ions (Na+) and one thiosulfate ion (S2O3^2-).

22. Why is sodium thiosulfate called a "thio" compound?

Sodium thiosulfate is called a "thio" compound because it contains sulfur in place of oxygen. The prefix "thio-" indicates that an oxygen atom has been replaced by a sulfur atom in the structure.

23. How does the structure of the thiosulfate ion differ from that of the sulfate ion?

The thiosulfate ion (S2O3^2-) differs from the sulfate ion (SO4^2-) in that one oxygen atom in sulfate is replaced by a sulfur atom. This results in a chain-like structure with a sulfur-sulfur bond, rather than the tetrahedral structure of sulfate.

24. What is the oxidation state of sulfur in sodium thiosulfate?

In sodium thiosulfate (Na2S2O3), sulfur exists in two different oxidation states. One sulfur atom has an oxidation state of +6, while the other has an oxidation state of -2.

25. How does the structure of sodium thiosulfate contribute to its reducing properties?

The reducing properties of sodium thiosulfate stem from its structure, particularly the presence of sulfur in a lower oxidation state (-2) alongside sulfur in a higher oxidation state (+6). This allows it to easily donate electrons in redox reactions.

26. What is the primary industrial method for preparing sodium thiosulfate?

The primary industrial method for preparing sodium thiosulfate involves the reaction of sodium sulfite with elemental sulfur. The reaction can be represented as: Na2SO3 + S → Na2S2O3

27. Why is sodium thiosulfate considered a metastable compound?

Sodium thiosulfate is considered metastable because, while it's stable under normal conditions, it can decompose when heated or in the presence of acids. This metastability is due to the unique bonding arrangement in the thiosulfate ion.

28. How does sodium thiosulfate behave at high temperatures?

At high temperatures, sodium thiosulfate decomposes. The decomposition products can include sodium sulfate, sodium sulfide, and sulfur dioxide, depending on the specific conditions.

29. How does the concentration of sodium thiosulfate affect its reducing power?

The reducing power of sodium thiosulfate increases with concentration. Higher concentrations provide more thiosulfate ions available for electron donation, enhancing its effectiveness as a reducing agent.

30. What is the significance of sodium thiosulfate in redox titrations?

In redox titrations, sodium thiosulfate serves as a standard reducing agent. Its reaction with oxidizing agents like iodine is quantitative and rapid, making it ideal for precise analytical measurements.

31. Why is sodium thiosulfate used in photography?

Sodium thiosulfate is used in photography as a "fixer" because it can form soluble complexes with silver halides. This process removes unexposed silver halides from photographic film or paper, stabilizing the image.

32. What is the role of sodium thiosulfate in gold extraction?

In gold extraction, sodium thiosulfate can be used as an alternative to cyanide in leaching gold from ores. It forms stable gold-thiosulfate complexes, allowing for the separation of gold from other minerals.

33. What is the environmental impact of sodium thiosulfate usage?

Sodium thiosulfate is generally considered environmentally friendly. It's non-toxic and biodegradable. However, its oxygen-depleting properties in water can potentially affect aquatic life if released in large quantities.

34. How does sodium thiosulfate interact with chlorine in water treatment?

Sodium thiosulfate reacts with chlorine in water treatment to neutralize excess chlorine. It reduces chlorine to chloride ions, making it useful for dechlorination in aquariums and water systems.

35. What is the role of sodium thiosulfate in the sodium-thiosulfate clock reaction?

In the sodium-thiosulfate clock reaction, sodium thiosulfate reacts with hydrochloric acid to form colloidal sulfur. The time taken for the solution to become opaque is used to study reaction kinetics and factors affecting reaction rates.

36. How does sodium thiosulfate interact with iodine in a titration?

In a titration, sodium thiosulfate reacts with iodine to form iodide ions and tetrathionate ions. The reaction is: 2Na2S2O3 + I2 → 2NaI + Na2S4O6. This reaction is the basis for iodometric titrations in analytical chemistry.

37. What is the crystal structure of sodium thiosulfate pentahydrate?

Sodium thiosulfate pentahydrate (Na2S2O3·5H2O) crystallizes in a monoclinic system. The crystal structure consists of sodium ions, thiosulfate ions, and water molecules arranged in a specific three-dimensional pattern.

38. How does sodium thiosulfate interact with heavy metal ions?

Sodium thiosulfate can form complex ions with various heavy metal ions. This property is useful in analytical chemistry for the separation and identification of metal ions, and in some cases, for the treatment of heavy metal pollution.

39. How does sodium thiosulfate contribute to the fire-resistant properties of certain materials?

Sodium thiosulfate can be used as a fire retardant. When heated, it releases water and forms a protective layer of sodium sulfate, which can help inhibit combustion and slow the spread of fire.

40. What is the role of sodium thiosulfate in the paper industry?

In the paper industry, sodium thiosulfate is used to remove excess chlorine after bleaching processes. It helps prevent yellowing of paper and degradation of cellulose fibers caused by residual chlorine.

41. How does sodium thiosulfate contribute to the preservation of leather?

Sodium thiosulfate is used in leather tanning processes to neutralize excess chlorine from chlorinated water. This prevents damage to the leather and helps maintain its quality and durability.

42. What is the significance of sodium thiosulfate in wine production?

In wine production, sodium thiosulfate can be used to remove excess sulfur dioxide, which is often added as a preservative. This helps in adjusting the sulfite levels in wine to meet regulatory standards and improve taste.

43. How does sodium thiosulfate interact with halogens other than chlorine and iodine?

Sodium thiosulfate can react with other halogens like bromine and fluorine, acting as a reducing agent. However, the reactions with these halogens are generally less commonly utilized compared to its reactions with chlorine and iodine.

44. What is the role of sodium thiosulfate in soil chemistry?

In soil chemistry, sodium thiosulfate can be used to measure soil sulfate levels. It can also be used to remediate soils contaminated with certain heavy metals by forming soluble complexes with these metals.

45. How does the presence of sodium thiosulfate affect the conductivity of a solution?

The presence of sodium thiosulfate increases the electrical conductivity of a solution. When dissolved, it dissociates into sodium and thiosulfate ions, which can carry electrical charge through the solution.

46. What is the significance of sodium thiosulfate in the production of thiourea?

Sodium thiosulfate is a key reagent in the industrial production of thiourea. It reacts with ammonium thiocyanate to form thiourea, which has various applications in agriculture and industry.

47. How does sodium thiosulfate interact with enzymes in biological systems?

Sodium thiosulfate can interact with certain enzymes in biological systems. For example, it can serve as a substrate for thiosulfate reductase enzymes, playing a role in sulfur metabolism in some organisms.

48. What is the role of sodium thiosulfate in the treatment of calciphylaxis?

Sodium thiosulfate is used in the treatment of calciphylaxis, a rare but serious condition involving calcium deposition in blood vessels. It acts as a calcium chelator and antioxidant, helping to dissolve calcium deposits and reduce inflammation.

49. How does the structure of sodium thiosulfate contribute to its ability to form complexes?

The structure of the thiosulfate ion, with its sulfur-sulfur bond and multiple oxygen atoms, allows it to act as a multidentate ligand. This enables sodium thiosulfate to form stable complexes with various metal ions.

50. What is the significance of sodium thiosulfate in the production of synthetic fibers?

In the production of synthetic fibers, sodium thiosulfate is used to neutralize excess oxidizing agents used in the manufacturing process. This helps prevent damage to the fibers and ensures consistent quality.

51. How does sodium thiosulfate interact with atmospheric pollutants?

Sodium thiosulfate can react with certain atmospheric pollutants, particularly oxidizing agents like ozone or nitrogen oxides. This property makes it useful in some air purification systems and in studying atmospheric chemistry.

52. What is the role of sodium thiosulfate in the food industry?

In the food industry, sodium thiosulfate is used as an approved food additive (E539). It serves as an antioxidant and sequestrant, helping to preserve food quality and extend shelf life.

53. How does the presence of sodium thiosulfate affect the freezing point of water?

Like other dissolved salts, sodium thiosulfate lowers the freezing point of water. This colligative property depends on the concentration of the solution and is related to the number of particles dissolved.

54. What is the significance of sodium thiosulfate in the study of reaction kinetics?

Sodium thiosulfate is often used in studying reaction kinetics, particularly in clock reactions. The rate of its reaction with acids can be easily observed, making it useful for investigating factors that affect reaction rates.

55. How does sodium thiosulfate contribute to the removal of chloramines in water treatment?

Sodium thiosulfate effectively removes chloramines from water by reducing them to chloride ions. This is particularly important in aquarium maintenance and in preparing water for brewing and other sensitive processes.

56. What is the role of sodium thiosulfate in the production of certain dyes?

In dye production, sodium thiosulfate can be used as a reducing agent to convert certain dye precursors into their active forms. It's also used in some dyeing processes to neutralize excess oxidizing agents.

57. How does the thermal decomposition of sodium thiosulfate differ from its reaction with acids?

Thermal decomposition of sodium thiosulfate produces sodium sulfate and sodium sulfide, while its reaction with acids produces sulfur dioxide, water, and elemental sulfur. The thermal decomposition doesn't involve the formation of a gas, unlike the acid reaction.

58. What is the significance of sodium thiosulfate in the production of thioacetamide?

Sodium thiosulfate is a key reagent in the industrial production of thioacetamide. It reacts with acetamide to form thioacetamide, which has various applications in organic synthesis and as a sulfiding agent.

59. How does sodium thiosulfate contribute to the stability of certain colloidal systems?

Sodium thiosulfate can act as a stabilizer for certain colloidal systems, particularly those involving metal nanoparticles. It can form a protective layer around particles, preventing aggregation and maintaining colloidal stability.

60. What is the role of sodium thiosulfate in the vulcanization of rubber?

In the vulcanization of rubber, sodium thiosulfate can be used as an accelerator. It helps to speed up the cross-linking process between rubber molecules and sulfur, improving the physical properties of the final rubber product.