According to Lewis theory, the total number of $\sigma$ bond-pairs and lone pair of electrons around the central atom of $\mathrm{XeO}_6{ }^{4-}$ ion is $\_\_\_\_$ .

$$ \text { Consider the following sequence of reactions to give the major product }(\mathrm{X}) $$

P g of the major product $(\mathrm{X})$ formed is reacted with $\mathrm{NaHCO}_3$ solution to liberate a gas which occupied $11.2 \mathrm{dm}^3$ at STP.

$$ \mathrm{P}=\text {______________ g. } $$

(Given molar mass in $\mathrm{g} \mathrm{mol}^{-1} \mathrm{H}: 1, \mathrm{C}: 12, \mathrm{O}: 16, \mathrm{Cl}: 35.5$ )

2.0 g of a bromo hydrocarbon $(\mathrm{X})$ was subjected to Carius analysis, gave 3.36 g of AgBr . The percentage of carbon in the compound $(\mathrm{X})$ is $26.7 \%$. Total number of carbon atoms in the empirical formula for compound $(\mathrm{X})$ is $\_\_\_\_$ .

(Given molar mass in $\mathrm{g} \mathrm{mol}^{-1} \mathrm{H}: 1, \mathrm{C}: 12, \mathrm{Br}: 80, \mathrm{Ag}: 108$ )

The pH of a solution obtained by mixing 5 mL of $0.1 \mathrm{M} \mathrm{NH}_4 \mathrm{OH}$ solution with 250 mL of $0.1 \mathrm{M} \mathrm{NH}_4 \mathrm{Cl}$ solution is $\_\_\_\_$ $\times 10^{-2}$.(Nearest integer) Given: $\mathrm{pK}_{\mathrm{b}}\left(\mathrm{NH}_4 \mathrm{OH}\right)=4.74$

$$ \begin{aligned} & \log 2=0.30 \\ & \log 3=0.48 \\ & \log 5=0.70 \end{aligned} $$