Calculate the millimoles of ${{\mathrm{SeO}}_3}^{2-}$ in solution on the basis of following data:

$70 \mathrm{ml}$ of $\frac{\mathrm{M}}{60}$ solution of ${\mathrm{KBrO}}_3$ was added to ${{\mathrm{SeO}}_3}^{2-}$ solution. The bromine evolved was removed by boiling and excess of ${\mathrm{KBrO}}_3$ was back titrated with $12.5 \mathrm{ml}$ of $\frac{\mathrm{M}}{25}$ solution of ${\mathrm{NaAsO}}_2.$

The reactions are given below.

$\left(\mathrm{a}\right)$ ${\mathrm{SeO}}_3{}^{2-}+{\mathrm{BrO}}_3{}^{-}+{\mathrm{H}}^{+}\to {\mathrm{SeO}}_4{}^{2-}+{\mathrm{Br}}_2+{\mathrm{H}}_2\mathrm{O}$

$\left(\mathrm{b}\right)$ ${\mathrm{BrO}}_3^{-}+{\mathrm{AsO}}_2^{-}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{Br}}^{-}+{\mathrm{AsO}}_4^{3-}+{\mathrm{H}}^{+}$

In the following reaction:

$\mathrm{A}+2\mathrm{B}+3\mathrm{C}\rightleftharpoons \mathrm{A}{\mathrm{B}}_2{\mathrm{C}}_3$
$6.0 \mathrm{g}$ of $\mathrm{A}$, $6.0\times {10}^{23}\mathrm{ }$ atoms of $\mathrm{B}$ and $0.036 \mathrm{mol}$ of $\mathrm{C}$ reacted and formed $4.8 \mathrm{g}$ of compound $\mathrm{A}{\mathrm{B}}_2{\mathrm{C}}_3$. If the atomic mass of $\mathrm{A}$  and $\mathrm{C}$ are $60$ and $80 \mathrm{amu}$, respectively. What is the atomic mass of $\mathrm{B}$ in $\mathrm{amu}$? (Avogadro number$=6\times {10}^{23}$)

Galena (an ore) is partially oxidized by passing air through it at high temperature. After some time, the passage of air is stopped, but the heating is continued in a closed furnace such that the contents undergo self-reduction. The weight (in $\mathrm{kg}$) of $\mathrm{Pb}$ produced per $\mathrm{kg}$ of ${\mathrm{O}}_2$ consumed is ____. (Atomic weights in $\mathrm{g}\mathrm{ }{\mathrm{mol}}^{-1}: \mathrm{O}=16,\mathrm{ }\mathrm{S}=32,\mathrm{ }\mathrm{Pb}=207$)

Give the answer to the nearest integer value.

The ammonia is prepared by treating ammonium sulphate with calcium hydroxide is completely used by ${\mathrm{NiCl}}_2\mathbf{·}6{\mathrm{H}}_2\mathrm{O}$ to form a stable coordination compound. Assume that, both the reactions are $100\%$ completed. If $1584 \mathrm{g}$ of ammonium sulphate and $952 \mathrm{g}$ of ${\mathrm{NiCl}}_2\mathbf{·}6{\mathrm{H}}_2\mathrm{O}$ are used in the preparation, the combined weight (in grams) of gypsum and the nickel ammonia coordination compound produced is ____.

Atomic weights in $\mathrm{g}\mathrm{ }{\mathrm{mol}}^{-1}$:

$$\begin{gathered} \mathrm{H}=1;\mathrm{ }\mathrm{N}=14\mathrm{ } \\ \mathrm{O}=16; \mathrm{S}=32\mathrm{ } \\ \mathrm{Cl}=35.5;\mathrm{ }\mathrm{Ca}=40\mathrm{ } \\ \mathrm{Ni}=59 \end{gathered}$$

${\mathrm{NaClO}}_3$ is used, even in spacecrafts, to produce ${\mathrm{O}}_2.$ The daily consumption of pure ${\mathrm{O}}_2$ by a person in $492 \mathrm{L}$ at $1$ atm, $300\mathrm{K}.$ How much amount of ${\mathrm{NaClO}}_3,$ in grams, is required to produce ${\mathrm{O}}_2$ for the daily consumption of a person at $1$ atm, $\mathrm{}300\mathrm{K}$ ? 

${\mathrm{NaClO}}_3\left(\mathrm{s}\right)+\mathrm{Fe}\left(\mathrm{s}\right)\to {\mathrm{O}}_2\left(\mathrm{g}\right)+\mathrm{NaCl}\left(\mathrm{s}\right)+\mathrm{FeO}\left(\mathrm{s}\right)$
$\mathrm{R}=0.082 \mathrm{L} \mathrm{atm} {\mathrm{mol}}^{-1} {\mathrm{K}}^{-1}$

Give answer to the nearest integer value.