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During the borax bead test, a transparent glassy bead is formed, which gives characteristic colors wp Block Elements Chemistry Question

Question

During the borax bead test, a transparent glassy bead is formed, which gives characteristic colors with transition metals. The blue bead formed with $Co^{2+}$ is chemically:

Answer: B

💡 Solution & Explanation

Heating borax produces a glassy bead of sodium metaborate ($NaBO_2$) and boric anhydride ($B_2O_3$). The basic metal oxide reacts with acidic $B_2O_3$ to form a colored metal metaborate. For Cobalt, it forms $Co(BO_2)_2$, which is blue.

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