${\mathrm{BX}}_3+{\mathrm{NH}}_3\stackrel{\mathrm{R}.\mathrm{T}.}{\to }{\mathrm{BX}}_3 .{\mathrm{NH}}_3+$ Heat of adduct formation $\left(∆\mathrm{H}\right)$

The numerical value of $∆\mathrm{H}$ is found to be maximum for :

(1) ${\mathrm{BF}}_3$                               

(2) ${\mathrm{BCl}}_3$

(3) ${\mathrm{BBr}}_3$                             

(4) ${\mathrm{BI}}_3$

Borax is converted into crystalline boron by the following steps:

          $\mathrm{Borax}\stackrel{\mathrm{X}}{\to }{\mathrm{H}}_3{\mathrm{BO}}_3\stackrel{∆}{\to }{\mathrm{B}}_2{\mathrm{O}}_3\underset{∆}{\overset{\mathrm{Y}}{\to }}\mathrm{B}$

X and Y are respectively :

1. HCl, Mg                                 
2. HCl, C
3. C, Al 
4. HCl, Al

The dissolution of $\mathrm{Al}(\mathrm{OH}{)}_3$ in a solution of $\mathrm{NaOH}$ results in the formation of -

1. ${\left[\mathrm{Al}{\left({\mathrm{H}}_2\mathrm{O}\right)}_4{\left(\mathrm{OH}\right)}_2\right]}^{+}$       

2. $\left[\mathrm{Al}{\left({\mathrm{H}}_2\mathrm{O}\right)}_3{\left(\mathrm{OH}\right)}_3\right]$

3. ${\left[\mathrm{Al}{\left({\mathrm{H}}_2\mathrm{O}\right)}_2{\left(\mathrm{OH}\right)}_4\right]}^{-}$     

4. $\left[\mathrm{Al}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6{\left(\mathrm{OH}\right)}_3\right]$

Choose the correct squence for the geometry of thr given molecules Borazone, Borazole, ${\mathrm{B}}_3{\mathrm{O}}_6^{3-}, {\mathrm{Fe}}_2{\mathrm{Cl}}_{6,}$ trimer of FCN. ('P' stands for planar and 'NP' stdans for non-planar)

(1) NP, NP, NP, P, P                                 

(2) P, P, NP, NP, P

(3) NP, NP, NP, P, NP                                 

(4) NP, P, P, NP, P

The incorrect statement among the following regarding borax is-

1. It is a useful primary standard for titrating against acids. 

2. One molecule of borax contains 4 \(B — O — B\) bonds.

3. Aqueous solution of borax can be used as a buffer.

4. It is made up of two triangular \(BO_{3}\) units and two tetrahedral \(BO_{4}\) units.

$\mathrm{B}(\mathrm{OH}{)}_3+\mathrm{NaOH}\underset{}{\to }{\mathrm{NaBO}}_2+\mathrm{Na}\left[\mathrm{B}{\left(\mathrm{OH}\right)}_4\right]+{\mathrm{H}}_2\mathrm{O}$

How can this reaction is made to proceed in forward direction?

(a) addition of cis1, 2 diol                   (b) addition of borax

(c) addition of trans1, 2 diol                (d) addition of ${\mathrm{Na}}_2{\mathrm{HPO}}_4$

The species among the following that does not exist is-

1. ${\left(\mathrm{Sn}{F}_6\right)}^{2-}$

2. ${\left({\mathrm{GeCl}}_6\right)}^{2-}$

3. ${\left({\mathrm{CCl}}_6\right)}^{2-}$

4. ${\left({\mathrm{SiF}}_6\right)}^{2-}$

The incorrect statement regarding above reactions is :

(a) Al shows amphoteric character

(b) Gas 'P' and 'Q' are different

(d) Both X and Y are water soluble

(d) Gas Q is inflammable

The incorrect statement regarding above reactions is :

${\mathrm{BF}}_3+{\mathrm{LiAlH}}_4\stackrel{\mathrm{Ether}}{\to }\left(\mathrm{X}\right)+\mathrm{LiF}+{\mathrm{AlF}}_3$

(1) Twelve electrons are involed in bonding 

(2) Four, two centre-two electron bonds

(3) Two, three centre-two electron bonds 

(4) X does not react with ${\mathrm{NH}}_3$

${\left({\mathrm{si}}_2{\mathrm{O}}_5\right)}_{\mathrm{n}}^{2\mathrm{n}-}$ anion is obtained when :

(a) no oxygen of a ${\mathrm{SiO}}_4^{4-}$ tetrahedron is shared with another ${\mathrm{SiO}}_4^{4-}$ tetrahedron

(b) one oxygen of a ${\mathrm{SiO}}_4^{4-}$ tetrahedron is shared with another ${\mathrm{SiO}}_4^{4-}$ tetrahedron

(c) two oxygen of a ${\mathrm{SiO}}_4^{4-}$ tetrahedron is shared with another ${\mathrm{SiO}}_4^{4-}$ tetrahedron

(d) three oxygen of a ${\mathrm{SiO}}_4^{4-}$ tetrahedron is shared with another ${\mathrm{SiO}}_4^{4-}$ tetrahedron