Question
What happens when a mixture of cobalt oxide and borax is heated in a flame on a loop of platinum wire?
A.
A transparent white bead is formed.
B.
A bright pink coloured $$NaB{O_2}$$ bead is formed.
C.
A blue coloured $$Co{\left( {B{O_2}} \right)_2}$$ bead is formed.
D.
A red coloured $$Co{\left( {B{O_2}} \right)_2}$$ bead is formed.
Answer :
A blue coloured $$Co{\left( {B{O_2}} \right)_2}$$ bead is formed.
Solution :
\[N{{a}_{2}}{{B}_{4}}{{O}_{7}}\cdot 10{{H}_{2}}O\xrightarrow{\Delta }N{{a}_{2}}{{B}_{4}}{{O}_{7}}\] \[\xrightarrow{\Delta }2NaB{{O}_{2}}+{{B}_{2}}{{O}_{3}}\]
\[{{B}_{2}}{{O}_{3}}+CoO\to \underset{\begin{smallmatrix}
\text{Cobalt metaborate} \\
\text{(blue bead)}
\end{smallmatrix}}{\mathop{Co{{\left( B{{O}_{2}} \right)}_{2}}}}\,\]