Question

what is the role of potassium sodium tartrate in the feelings test

Answer 1

ANS.

****Fehling's A is a blue aqueous solution of copper (II) sulphate, while Fehling's B is a clear solution of aqueous potassium sodium tartrate (also known as Rochelle salt) and a strong alkali (commonly sodium hydroxide).

***Equal volumes of the two mixtures are mixed together to get the final Fehling's solution, which is a deep blue colour.

***In this final mixture, aqueous tartrate ions from the dissolved Rochelle salt chelate to Cu²⁺ (aq) ions from the dissolved copper(II) sulphate, as bidentate ligands giving the bistartratocuprate(II)^4- complex.

[******The tartarate ions, by complexing copper prevent the formation of Cu (OH)₂ from the reaction of CuSO₄.2H₂O and NaOH present in the solution.]