A plant virus is found to consist of uniform symmetrical particles of $150 \stackrel{\mathrm{o}}{\mathrm{A}}$ in diameter and $5000 \stackrel{\mathrm{o}}{\mathrm{A}}$ long. The specific volume of the virus is $\frac{0.75{ \mathrm{cm}}^3}{\mathrm{g}}.$ If the virus is considered to be a single particle, if its molecular weight is $\mathrm{x}\times {10}^7 \mathrm{g}$ then find $\mathrm{x}$.

Nitric acid can be produced from ammonia in three steps process.

$4{\mathrm{NH}}_3\left(\mathrm{g}\right)+5{\mathrm{O}}_2\left(\mathrm{g}\right)\to 4\mathrm{NO}\left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right) ...\left(1\right)$

$2\mathrm{NO}\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{NO}}_2\left(\mathrm{g}\right) ...\left(2\right)$

$3{\mathrm{NO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2{\mathrm{HNO}}_3\left(\mathrm{aq}.\right)+\mathrm{NO}\left(\mathrm{g}\right) ...\left(3\right)$

Calculate weight of ${\mathrm{NH}}_3\left(\mathrm{g}\right)$ required to produce $1260 \mathrm{kg}$ of ${\mathrm{HNO}}_3.$ When $\%$ Yield of $1^{\mathrm{st}},2^{\mathrm{nd}}$ and $3^{\mathrm{rd}}$ reactions are respectively $69\%,60\%$ and $68\%$ respectively.

$6.2 \mathrm{g}$ of a sample containing ${\mathrm{Na}}_2{\mathrm{CO}}_3,{\mathrm{NaHCO}}_3 \&$ non-volatile inert impurity on gentle heating loses $5\%$ of its weight due to formation of ${\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{CO}}_2$ as in reaction

$2{\mathrm{NaHCO}}_3\to {\mathrm{Na}}_2{\mathrm{CO}}_3+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2$ Residue is dissolved in water and formed $100 \mathrm{ml}$ solution and its $10 \mathrm{ml}$ portion requires $7.5 \mathrm{ml}$ of $0.2 \mathrm{M}$ aqueous solution of ${\mathrm{BaCl}}_2$ for complete precipitation of carbonates. Determine weight (in gram) of ${\mathrm{Na}}_2{\mathrm{CO}}_3$ in the original sample