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 a 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. The melting point of silica is very high.

${\mathrm{Na}}_2{\mathrm{B}}_4{\mathrm{O}}_7\cdot 10{\mathrm{H}}_2\mathrm{O}<mspace\; width="1em"></mspace>\underset{∆}{\overset{{740}^{\circ }\mathrm{C}}{\to }}<mspace\; width="1em"></mspace>2{\mathrm{NaBO}}_2+\left(\mathrm{X}\right)+10{\mathrm{H}}_2\mathrm{O}$
$\left(\mathrm{X}\right)+{\mathrm{CaF}}_2+{\mathrm{H}}_2{\mathrm{SO}}_4⟶\mathrm{Y}+{\mathrm{CaSO}}_4+{\mathrm{H}}_2\mathrm{O}$
$\left(\mathrm{Y}\right)+{\mathrm{NaBH}}_4⟶\left(\mathrm{Z}\right)+{\mathrm{NaBF}}_4$

Select the incorrect statement regarding compounds (X), (Y) and (Z).

1.  Compound (X) is ${\mathrm{B}}_2{\mathrm{O}}_3$ and compound (Z) contains two 3C - 2e bonds

2.  Compound (X) is ${\mathrm{B}}_2{\mathrm{O}}_3$ and compound (Y) contains one 3C - 2e bonds 

3.  Compound (Y) is Lewis acid and stable due to $p\pi -p\pi$ back bonding

4.  Compound (Z) reacts with excess of ${\mathrm{NH}}_3$ at high temperature gives inorganic graphite 

${\mathrm{BCl}}_3$ 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 $\mathrm{p\pi }-\mathrm{d\pi }$ 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 does not show inert pair effect

(1) Al

(2) Sn

(3) Pb

(4) Thallium

The element among the following that does not show the inert pair effect is:

1. Al

2. Sn

3. Pb

4. Tl

Assertion: The total number of coordinate bonds and covalent bonds in borazine is 3 and 12 respectively.

Reason: Its structure is similar to benzene.

1. Both Assertion & Reason are true and the reason is the correct explanation of the assertion.

2. Both Assertion & Reason are true but the reason is not the correct explanation of the assertion.

3. Assertion is a true statement but Reason is false.

4. Both Assertion and Reason are false statements.

Assertion: Boron always forms a covalent bond.

Reason: Boron has a diagonal relationship with silicon.

1. Both Assertion & Reason are true and the reason is the correct explanation of the assertion.
2. Both Assertion & Reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is a true statement but Reason is false.
4. Both Assertion and Reason are false statements.

Assertion: B-X bond length in ${\mathrm{BX}}_3$ is shorter than the expected value.

Reason: $p\mathrm{\pi }-\mathrm{p\pi }$ back bonding occurs between B and X.

1. Both Assertion & Reason are true and the reason is the correct explanation of the assertion.
2. Both Assertion & Reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is a true statement but Reason is false.
4. Both Assertion and Reason are false statements.

A compound X, of boron, reacts with ${\mathrm{NH}}_3$ on heating to give another compound Y which is called inorganic benzene. The compound X can be prepared by treating ${\mathrm{BF}}_3$ with Lithium aluminium hydride. The compounds X and Y are represented by the formulas -

Ionization enthalpy (${∆}_{\mathrm{i}}{\mathrm{H}}_1\mathrm{kJ}<mspace\; width="1em"></mspace>{\mathrm{mol}}^{-1}$) for the elements of Group 13 follows the order.