Acidified soln of sod. thio sulphate i.e. Na2S2O3 is unstable.......

Can u tell me y???

 

I am not sure but in acid medium thiosulphate ion is converted to S.

I say this bcoz, for studying the rate of reaction and its dependence on temp and conc we usually take the reaction b/w sodium thiosulphate and HCl and note the time for S to ppt.

 

Yar pls rate me if I am right

Ya, This is because in acidic medium the thiosulphate ion dispropitates to elemental sulphur and sulphur dioxide

In Hydrochloric acid

 

Na₂S₂O₃ + 2HCl   2NaCl + S +SO₂ + H₂O

 

 

it is a sodium salt of an unstable acid.it is a colourless crystalline solid consisting of 5 molecules of wateras water of crystallization.it is soluble in water.when heated above 223c it decomposes forming sodium sulphate and sodium pentasulphide.

dilute acids decompose it with evolution of so₂and percipitationof sulphur.

na₂s₂o₃+h₂so₄=na₂so₄+so₂+s+h₂o

it is used in the extraction of silver and gold.