MCQ
When borax is heated with $CoO$ on a platinum loop, blue coloured bead formed is largely due to
- A$B _{2} O _{3}$
- ✓$Co \left( BO _{2}\right)_{2}$
- C$CoB _{4} O _{7}$
- D$Co [ B _{4} O _{5}( OH )_{4}]$
✓
Answer
Correct option: B.
$Co \left( BO _{2}\right)_{2}$
b
$Na _{2} B _{4} O _{7} \cdot 10 H _{2} O \stackrel{\Delta}{\longrightarrow} Na _{2} B _{4} O _{7}+10 H _{2} O$
$Na _{2} B _{4} O _{7} \cdot 10 H _{2} O \stackrel{\Delta}{\longrightarrow} Na _{2} B _{4} O _{7}+10 H _{2} O$
$Na _{2} B _{4} O _{7} \stackrel{\Delta}{\longrightarrow} 2 NaBO _{2} \text { (sodium meta borate) }+ B _{2} O _{3}$
$B _{2} O _{3}+ CoO \rightarrow Co \left( BO _{2}\right)_{2} \text { (cobalt (II) meta borate) }$
$\quad\quad\quad\quad\quad\quad\quad$Blue Bead
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