Question

Statement I : Colourless cupric metaborate is reduced to cuprous metaborate in a luminous flame. Statement II : Cuprous metaborate is obtained by heating boric anhydride and copper sulphate in a non-luminous flame.

• A. Both true
• B. Both false
• C. I true, II false
• D. I false, II true

Hint:

The Borax Bead Test is a classical qualitative analysis technique. The color of the bead depends on whether the flame is oxidizing (blue) or reducing (yellow).

Answer 1

The Correct Option is B

Step 1: In the Borax Bead Test, Cupric metaborate ($Cu(BO_2)_2$) is blue/green in a non-luminous (oxidizing) flame.
Step 2: In a luminous (reducing) flame, cupric metaborate is reduced to red/opaque Cuprous metaborate ($Cu_2(BO_2)_2$) or metallic Copper.
Step 3: Statement I is false because cupric metaborate is blue/green, not colourless. Statement II is false because non-luminous flames are oxidizing, which would yield cupric ($Cu^{2+}$), not cuprous ($Cu^+$).