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MolSynapse / Question bank / p-Block Elements: Groups 13 and 14 / Boron compounds: diborane, boric acid, borax, boron halides
JEE Main levelSingle correct optionDifficulty 2 of 3pb016

A borax bead is heated in the flame with a trace of a cobalt(II) salt. The coloured compound formed in the bead and its colour are

  1. A, deep blue
  2. B, deep blue
  3. C, deep blue
  4. D, colourless

Answer: A

On heating, gives and then . The combines with the cobalt oxide to give the metaborate , which is deep blue (cobalt blue).
Practice p-Block Elements: Groups 13 and 14 More on Boron compounds: diborane, boric acid, borax, boron halides
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More questions on Boron compounds: diborane, boric acid, borax, boron halides