Question

The mineral colemanite is finely powdered and boiled with sodium carbonate solution. The precipitate of $CaC{O}_3$ and other two products $X$ and $Y$ are formed. On passing a current of $C{O}_2$, $Y$ produces $X$. Which of the following statement is correct about $X$?

• A. Oxidation state of boron in compound $X$ is $+1$
• B. It is used in bead test.
• C. It is a black crystalline solid.
• D. none of these

Answer 1

The correct option is B It is used in bead test.

The mineral colemanite is finely powdered and boiled with sodium carbonate solution.

$C{a}_2{B}_6{O}_{11}+2N{a}_{2}C{O}_3\underset{\left(ii\right)H_{2}O}{\overset{\left(i\right)Fuse}{\to }}2CaC{O}_3\downarrow +\underset{X}{N{a}_2{B}_4{O}_7}+\underset{Y}{2NaB{O}_2}$
On passing a current of CO2, Y produces X.

$\underset{Y}{4NaB{O}_2}+C{O}_2\to \underset{X}{N{a}_2{B}_4{O}_7}+N{a}_{2}C{O}_3$
$\underset{X}{N{a}_2{B}_4{O}_7}$ is used in borax bead test.

$\underset{X}{N{a}_2{B}_4{O}_7}\stackrel{heat}{\to }2NaB{O}_2+B_2{O}_3\text{glassy bead}$