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 $X$. What is the oxidation state of boron in compound $Y$?

• A. $+1$
• B. $+3$
• C. $+5$
• D. $0$

Answer 1

Answer: (B)

$+3$

The oxidation state of $boron$ in compound Y $NaB{O}_2$ is +3. The oxidation state of $Na$ is $+1$. The oxidation state of $oxygen$ is $-2$.
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.

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