Sodium Thiosulphate IIT JEE Study Material

Sodium Thiosulphate

Sodium Thiosulphate also called as thiosulfuric acid or disodium salt is an inorganic salt that is also available in the pentahydrates. This chemical substance has a chemical formula of Na2S2O3. It appears as a bright white colorless crystal or even in powder form. The substance is known to possess Alkaline nature when decomposed to sulfide and sulfate in the air.

Sodium thiosulfate readily dissolves in water giving thiosulfate ions, one of useful reducing agents. The Copper (II) sulfate dissolves to give the cupric ion; with regards to a redox reaction with the thiosulfate, the cupric particles acts like oxidizing agents.

Properties of Sodium Thiosulphate

Sodium Thiosulphate possesses various chemical and physical properties as given below

  • Sodium Thiosulphate appears as a white translucent colorless crystal and is an inorganic compound
  • It is water-soluble substance and is also soluble in oil of turpentine but not in the alcohol.
  • The substance has a melting point of about 48 to 52 C
  • This chemical substance is highly stable in nature and is said to be incompatible with some of the strong oxidizing agents and strong acids
  • Thiosulfate anion readily reacts with the dilute acids producing sulfur, sulfur dioxide and also water
  • The chemical has a density measuring about 1.667 g/mL

 

Structure of Sodium Thiosulphate

Sodium Thiosulphate

Sodium Thiosulphate has a chemical formula of Na2S2O3 and the molar mass of about 158.11 g/mol. The substance well exists in the form of pentahydrate salts (Na2S2O3.5H2O), having a molar mass measuring about 248.18 g/mol. The sodium Thiosulphate is an ionic compound which consists of two cations of sodium atom (Na+) and a negatively charged anion of thiosulfate (S2O3-). Here the central atom consisting of sulfur bonds to the three oxygen atoms and also an another atom of sulfur, all these through a single and also double bonds possessing resonance character. The solid also exists in a monoclinic crystalline structure.

The thiosulfate anion is usually a tetrahedral structure and, is obtained by the replacement of one of the atoms of oxygen by the use of sulfur atom in the sulfate anion.

Uses and Applications of Sodium Thiosulphate

We find various applications of sodium thiosulphate in different fields such as medicine, photography, gold extraction and many other areas. The other uses of it are below-

  • Sodium thiosulfate is used in the manufacture of patinas
  • In industries, the chemical is used for the dechlorination of small water bodies like ponds, aquariums, etc
  • In photography, the chemical is used as a fixing agent to dissolve the silver salts from the negatives
  • The chemical can be utilized as a cleansing agent when dissolved in a vast quantity of warm water
  • It is well used as an antidote agent concerning the cyanide poisoning
  • In medical field, it is employed in the pharmaceutical preparations such as anionic surfactant aiding in dispersion

Apart from the above uses, the chemical substance also finds its applications in the water treatment, leather tanning, neutralizing bleach, gold extraction, photographic film processing, and also in chemical heating pads.


Practise This Question

For the non - stoichiometric reaction, 2A+B C + D, the following kinetic data were obtained in three separate experiments, all at 298 K. 

 InitialInitialInitial rate of concentrationconcentrationformation of C [A][B](mol L1s1)(i)0.1 M0.1 M1.2×103(ii)0.1 M0.2 M1.2×13(iii)0.2 M0.1 M2.4×103

The rate law for the formation of C is