Question

Colour of compound obtained when cu 2+ reacts with pottasium ferrocyanide

Answer 1

red-brown in colour

Potassium ferrocyanide precipitates red-brown copper(II) ferrocyanide from Cu2+ solutions:

2Cu+2(aq)+[Fe(CN)6]4−(aq)↽−−⇀Cu2[Fe(CN)6](s)(4)

(4)2Cu2+(aq)+[Fe(CN)6]4−(aq)↽−−⇀Cu2[Fe(CN)6](s)

Cu5ppt.gif

This test is very sensitive. The precipitate is soluble in aqueous ammonia.

Note: Many metal ions form ferrocyanide precipitates, so potassium ferrocyanide is not a good reagent for separating metal ions. It is used more commonly as a confirmatory test.