Borax Bead Test is carried out when the original mixture is coloured. It is done with the help of a clean platinum wire on which a small loop is made at the end. When borax is heated on platinum wire

Question

Borax Bead Test is carried out when the original mixture is coloured. It is done
with the help of a clean platinum wire on which a small loop is made at the end.
When borax is heated on platinum wire loop a transparent glass like bead is 
obtained. The hot bead is brought in contact with salt till it reacts with fused
borax and colour is imparted to the bead. Bead colour is noted.
Colour of the bead | Ion
1. Blue green | Cu2+
2. Yellow | Fe3+
3. Green | Cr3+
4. Violet | Mn2+
5. Dark blue | Co2+
6. Brown | Ni2+

Prashant Kotian · Accepted Answer

Correct answer: C. Step 1: The reaction of bismuth(III) ions with iodide ions (I-) initially forms a dark brown/black precipitate of bismuth(III) iodide (BiI3). Step 2: The black BiI3 precipitate reacts with excess iodide ions to form a highly stable, soluble tetraiodobismuthate(III) complex anion: BiI3 + I- -> [BiI4]-. Step 3: The [BiI4]- complex solution exhibits a characteristic orange/yellow-orange color. This confirms the presence of Bi3+, matching option (b).

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