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When borax is heated with CoO on a platinum loop, blue coloured bead formed is largely due to : (1) B2O3 (2) Co(BO2)2 (3) CoB4O7 (4) Co[B4O5(OH)4]

1. B2O3
2. Co(BO2)2
3. CoB4O7
4. Co[B4O5(OH)4]

Correct answer: Co(BO2)2

Solution

The blue bead formed when borax is heated with CoO is primarily due to the formation of cobalt borate, specifically Co(BO2)2, which gives the characteristic blue color due to the presence of cobalt ions in the borate matrix.

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