p-Block Elements

Oleum, i.e. $\mathrm{H}_2 \mathrm{S}_2 \mathrm{O}_7$ can be prepared by adsorption of $\mathrm{SO}_3$ in conc. $\mathrm{H}_2 \mathrm{SO}_4$ as follows :

$\mathrm{SO}_3+\mathrm{H}_2 \mathrm{SO}_4 \longrightarrow \underset{\text { Oleum }}{\mathrm{H}_2 \mathrm{S}_2 \mathrm{O}_7}$

It's structure is as follows :

Thus, it has no $\mathrm{O}-\mathrm{O}$ bond and has $2-\mathrm{OH}$ groups. Thus, option (a) is the correct.

Neil Bartlett prepared a red compound, $\mathrm{O}_2^{+}[\mathrm{PtF}_6]^{-}$ by reacting platinum hexafluoride $(\mathrm{PtF}_6)$ with oxygen.

He found that ionisation energy of $\mathrm{Xe}(1170 \mathrm{~kJ} \mathrm{~mol}^{-1})$ is nearly equal to that of molecular oxygen $(1175 \mathrm{~kJ} \mathrm{~mol}^{-1})$ available. Therefore, he was able to form compound of xenon.

$\mathrm{Xe}+\mathrm{PtF}_6 \longrightarrow \mathrm{Xe}^{+}\left[\mathrm{PtF}_6\right]$, On the other hand $\mathrm{He}$ and $\mathrm{Ne}$ has very high value of ionisation energy.

Therefore, only Xe can participate in chemical reactions and form compounds.

Hence, option (a) is the correct.

As the size of the halogen atom increases from $\mathrm{F}$ to $\mathrm{I}, \mathrm{H}-X$ bond length in halogen acids also increases from $\mathrm{H}-\mathrm{F}$ to $\mathrm{HI}$.

$(\mathrm{HF}<\mathrm{HCl}<\mathrm{HBr}<\mathrm{HI})$. The increase in $\mathrm{H} X$ bond length decreases the strength of $\mathrm{H} X$ bond from $\mathrm{HF}$ to $\mathrm{HI}(\mathrm{HF}>\mathrm{HCl}>\mathrm{HBr}>\mathrm{HI})$.

Due to successive decrease in the strength of $\mathrm{H} X$ bonds, bond dissociation enthalpy decreases from $\mathrm{HF}$ to $\mathrm{HI}$.

Hypophosphoric acid $\left(\mathrm{H}_4 \mathrm{P}_2 \mathrm{O}_6\right)$ does not contain $\mathrm{P}-\mathrm{O}-\mathrm{P}$ bond whereas, isohypophosphoric acid $\left(\mathrm{H}_4 \mathrm{P}_2 \mathrm{O}_6\right)$, diphosphorus acid $\left(\mathrm{H}_4 \mathrm{P}_2 \mathrm{O}_5\right)$ and diphosphoric acid $\left(\mathrm{H}_4 \mathrm{P}_2 \mathrm{O}_7\right)$ all contain $\mathrm{P}-\mathrm{O}-\mathrm{P}$ bonds. The structures of the following oxyacids of phosphorus is shown below:

$\mathop {8N{H_3}}\limits_{(Excess)} + 3C{l_2}\buildrel {} \over \longrightarrow 6NH_4Cl+N_2$

$N{H_3} + \mathop {3C{l_2}}\limits_{(Excess)} \buildrel {} \over \longrightarrow NCl_3+3HCl$

Hence,

$\begin{aligned} & X=6 \mathrm{NH}_4 \mathrm{Cl}+\mathrm{N}_2 \\ & Y=\mathrm{NCl}_3+3 \mathrm{HCl} \end{aligned}$

The products of the reaction of copper with $\mathrm{HNO}_3$ depends upon the concentration of $\mathrm{HNO}_3$ used.

Copper metal reacts with dilute $\mathrm{HNO}_3$ to form nitrogen (II) oxide (NO).

$3 \mathrm{Cu}+8 \mathrm{HNO}_3 \text { (dil.) } \longrightarrow 3 \mathrm{Cu}\left(\mathrm{NO}_3\right)_2+2 \mathrm{NO}+4 \mathrm{H}_2 \mathrm{O}$

Copper metal reacts with conc. $\mathrm{HNO}_3$ to form nitrogen (IV) oxide or nitrogen dioxide $(\mathrm{NO}_2)$

$\mathrm{Cu}+4 \mathrm{HNO}_3 \text { (conc.) } \longrightarrow \mathrm{Cu}\left(\mathrm{NO}_3\right)_2+2 \mathrm{NO}_2+2 \mathrm{H}_2 \mathrm{O}$

A halate will be formed from halogen and the greenish yellow gas is $\mathrm{Cl}_2$.

The halate which is used in fireworks and safety matches is $\mathrm{KClO}_3$. The reaction is as follow

$3 \mathrm{Cl}_2+6 \mathrm{KOH} \longrightarrow \mathrm{KClO}_3+5 \mathrm{HCl}+3 \mathrm{H}_2 \mathrm{O}$

Assertion is true but reason is false. $\mathrm{N}_2$ is less reactive than $\mathrm{P}_4$ due to high value of bond dissociation energy, which is because of the presence of triple bond between two $\mathrm{N}$-atoms of $\mathrm{N}_2$ molecule.

Both assertion and reason is correct and reason is the correct explanation of the assertion. $\mathrm{NaCl}$ reacts with concentrated $\mathrm{H}_2 \mathrm{SO}_4$ to give colourless fumes with pungent smell. This pungent smell is due to formation of $\mathrm{HCl}$.

$\mathrm{NaCl}+\mathrm{H}_2 \mathrm{SO}_4 \longrightarrow \mathrm{Na}_2 \mathrm{SO}_4+2 \mathrm{HCl}$

But on adding $\mathrm{MnO}_2$, the fumes become greenish yellow due to formation of chlorine gas.