Easy MCQ +4 / -1 PYQ · JEE Mains 2022

When borax is heated with $\mathrm{CoO}$ on a platinum loop, blue coloured bead formed is largely due to :

  1. A $\mathrm{B}_{2} \mathrm{O}_{3}$
  2. B $\mathrm{Co}\left(\mathrm{BO}_{2}\right)_{2}$ Correct answer
  3. C $\mathrm{CoB}_{4} \mathrm{O}_{7}$
  4. D $\mathrm{Co}\left[\mathrm{B}_{4} \mathrm{O}_{5}(\mathrm{OH})_{4}\right]$

Solution

$\mathrm{Na}_{2} \mathrm{~B}_{4} \mathrm{O}_{7} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{NaBO}_{2}+\mathrm{B}_{2} \mathrm{O}_{3}$ <br/><br/>$\mathrm{B}_{2} \mathrm{O}_{3}+\mathrm{CoO} \rightarrow \mathrm{Co}\left(\mathrm{BO}_{2}\right)_{2}$

About this question

Subject: Chemistry · Chapter: p-Block Elements · Topic: Group 13: Boron Family

This question is part of PrepWiser's free JEE Main question bank. 300 more solved questions on p-Block Elements are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →