Borax

Q. When borax is heated with $\text{CoO}$ on a platinum loop, blue coloured bead formed is largely due to :

1. $\text{Co}{\left({\text{BO}}_2\right)}_2$
2. ${\text{B}}_2{\text{O}}_3$
3. $\text{Co}\left[{\text{B}}_4{\text{O}}_5\right(\text{OH}{)}_4]$
4. ${\text{CoB}}_4{\text{O}}_7$

Q.

$C{a}_2{B}_6{O}_{11}+N{a}_{2}C{O}_3\stackrel{Fused}{\to }\left(A\right)+\left(B\right)+CaC{O}_3\left(A\right)+C{O}_2\to \left(B\right)+N{a}_{2}C{O}_3\text{Solution}\left(B\right)+Conc.HCI\to NaCI+Acid\downarrow H_{2}O\left(C\right)\underset{heated}{\overset{Strongly}{\to }}\left(D\right)\text{Acid}\left(C\right)\left(D\right)+CuS{O}_4\underset{inflame}{\overset{Heated}{\to }}\text{Blue coloured}\left(E\right)\text{compound}\text{compound (E) is -}$

1. Cu2O

2. Cu(BO2)2

3. CuS

4. CuSO3

Q.

When Borax is dissolved in water

1. is formed

2. is formed only

3. is formed

4. and are formed

Q.

Borax is converted into crystalline boron by the following steps.

$Borax\stackrel{x}{⟶}{H}_{3}B{O}_3\stackrel{Heat}{⟶}{B}_2{O}_3\stackrel{y}{\underset{Heat}{⟶}}B$
X & Y are respectively

1. 

2. 

3. 

4. 

Q.

Aqueous solution of borax reacts with two mol of acids. This is because of -

1. Formation of 2 mol of only

2. Formation of 1 mol each of and

3. Formation of 1mol of only

4. Formation of 2 mol each of and , of which only reacts with acid

Q.

Borax is actually made of two tetrahedra and two triangular units joined together and should be written as: Na2[B4O5(OH)4]·8H2O

The correct statement/s about borax is/are:

a. Each boron atom has four B-O bonds

b. Each boron atom has three B-O bonds

c. Two boron atoms have four B-O bonds while other two have three B-O bonds

d. Each boron atom has one -OH groups

1. a

2. b

3. c

4. d

Q.

The crystalline form of borax has

1. Tetranuclear $\left[B_4{O}_5\right(OH{)}_4{]}^{2-}$

2. All boron atoms in the same plane

3. Equal number of $s{p}^2$ and $s{p}^3$ hybridized boron atoms

4. One terminal hydroxide per boron atom

Q.

$\begin{array}{cc}\text{List I}& \text{List II}\\ \text{A.}B{i}^{3+}⟶(BiO{)}^{+}& \text{p. Heat}\\ \text{B.}[Al{O}_2{]}^{-}⟶Al(OH{)}_3& \text{q. Hydrolysis}\\ \text{C.}Si{O}_4^{4-}⟶S{i}_2{O}_7^{6-}& \text{r. Acidification}\\ \text{D.}\left(B_4{O}_7^{2-}\right)⟶B(OH{)}_3& \text{s. dilution by water}\end{array}$

1. A – q B – r C – p D –q, r

2. A – r B – q C – p D –q, r

3. A – q, r B – q C – q D –q

4. None of the above

Q. Which is not true about borax?

1. It is a useful primary standard for titrating against acids.
2. One mole of borax contains 4 $B-O-B$ bonds.
3. An aqueous solution of borax can be used as a buffer.
4. It is made up of two triangular $B{O}_3$ units and two tetrahedral $B{O}_4$ units

Q.

Assertion (A) : $NaB{O}_3/O{H}^{-}$ can be used for oxidation of $C{r}^{3+}$ to $C{r}^{6+}$.
Reason (R) : In alkaline solution $NaB{O}_3$ produces $H_2{O}_2$.

1. (A) is correct; (R) is correct and (R) correctly explains (A).
2. (A) is correct; (R) is correct and (R) doesn't explain (A) correctly.
3. (A) is correct; (R) is incorrect.
4. (A) is incorrect; (R) is correct.