Question

Borax on heating strongly above its melting point melts to a liquid, then solidifies to a transparent mass commonly known as Borax Bead. The transparent glassy mass consists of :

• A. sodium pyroborate
• B. boric anhydride
• C. sodium metaborate
• D. mixture of sodium metaborate and boric anhydride

Answer 1

The correct option is D mixture of sodium metaborate and boric anhydride

If borax, $N{a}_2{B}_4{O}_7.10H_{2}O$ is heated on the platinum loop, a transparent colourless glass like bead of sodium metaborate $\left(NaB{O}_2\right)$ and boric anhydride $\left(B_2{O}_3\right)$ is formed.

$N{a}_2{B}_4{O}_7\stackrel{\Delta }{\to }2NaB{O}_2+B_2{O}_3$