Question

Given below are two statements : 

Statement I : Upon heating a borax bead dipped in cupric sulphate in a luminous flame, the colour of the bead becomes green. 

Statement II : The green colour observed is due to the formation of copper(I) metaborate. 

In the light of the above statements, choose the most appropriate answer from the options given below : 

(1) Both Statement I and Statement II are true 

(2) Statement I is true but Statement II is false 

(3) Both Statement I and Statement II are false 

(4) Statement I is false but Statement II is true

Answer 1

(3) Both Statement I and Statement II are false 

(Borax Bead Test) 

On treatment with metal salt, boric anhydride forms metaborate of the metal which gives different colours in oxidising and reducing flame. For example, in the case of copper sulphate, following reactions occur.

Two reactions may take place in reducing flame (Luminous flame)

(i) The blue-green Cu(BO₂)₂ is reduced to colourless cuprous metaborate as :

(ii) Cupric metaborate may be reduced to metallic copper and bead appears red opaque.