Which of the following cation can not give borax bead test?

(a) ${\mathrm{Cr}}^{3+}$                          (b) ${\mathrm{Co}}^{2+}$

(c) ${\mathrm{Ag}}^{+}$                           (d) ${\mathrm{Mn}}^{2+}$

The number of carbon atoms per unit cell of diamond unit cell is:-

1. 4

2. 8

3. 6

4. 1

Aluminium becomes passive in nitric acid because it-

1. Is a noble metal

2. Forms a thin film of oxide

3. Has a positive reduction potential

4.  None of the above

Hybridisation of boron in diborane is:

1.  $\mathrm{sp}$

2.  ${\mathrm{sp}}^2$

3.  ${\mathrm{sp}}^3$

4.  ${\mathrm{sp}}^3{\mathrm{d}}^2$

${\mathrm{BCl}}_3$ does not exist as dimer but ${\mathrm{BH}}_3$ exist as dimer $\left({\mathrm{B}}_2{\mathrm{H}}_6\right)$ because:

1.chlorine is more electronegative than hydrogen

2.there is $\mathrm{p\pi }-\mathrm{p\pi }$ back bonding in ${\mathrm{BCl}}_3$ but ${\mathrm{BH}}_3$ does not contain such multiple bonding

3.large sized chlorine atoms do not fit in between the small boron atoms whereas small sized hydrogen atoms get fitted between boron atoms

4.none of the above

Which of the following imparts green colour to flame?

1.  $\mathrm{B}{\left(\mathrm{OMe}\right)}_3$

2.  $\mathrm{Na}\left(\mathrm{OMe}\right)$

3.  $\mathrm{Al}{\left({\mathrm{OBr}}_2\right)}_3$

4.  $\mathrm{Sn}{\left(\mathrm{OH}\right)}_2$

Borax bead test is responded by:

1.  Divalent metals

2.  Heavy metals

3.  Light metals

4.  Metal which forms coloured metaborates

Fluorine is more electronegative than either boron or phosphorus. What conclusion can be drawn from the fact that ${\mathrm{BF}}_3$ has no dipole moment but ${\mathrm{PF}}_3$ has?

1.  ${\mathrm{BF}}_3$ is spherically symmetrical, ${\mathrm{PF}}_3$ is not

2.  ${\mathrm{BF}}_3$ molecule must be linear

3.  The atomic radius of P is larger than the atomic radius of B

4.  The ${\mathrm{BF}}_3$ molecule must be planar triangular

Borazine is obtained by reaction of:

1.  ${\mathrm{NH}}_3+{\mathrm{B}}_2{\mathrm{H}}_6 \mathrm{in} 2 : 1 \mathrm{ratio}$

2.  ${\mathrm{NH}}_3+{\mathrm{B}}_2{\mathrm{H}}_6 \mathrm{in} 1 : 2 \mathrm{ratio}$

3.  ${\mathrm{NH}}_3+{\mathrm{B}}_2{\mathrm{H}}_6 \mathrm{in} 1 : 4 \mathrm{ratio}$

4.  ${\mathrm{NH}}_3+{\mathrm{B}}_2{\mathrm{H}}_6 \mathrm{in} 4 : 1 \mathrm{ratio}$

Carbon dioxide is a gas but silica is a solid because:

1.  carbon dioxide is composed of discrete covalent ${\mathrm{CO}}_2$ molecules whereas silica has continuous

     tetrahedral structure

2.  ${\mathrm{CO}}_2$ molecules are lighter than ${\mathrm{SiO}}_2$ molecules

3.  ${\mathrm{CO}}_2$ is more acidic than ${\mathrm{SiO}}_2$

4.  melting point of silica is very high