A hydrocarbon $\left(\mathrm{C}_n \mathrm{H}_m\right)$ is burnt in air $\left(\mathrm{O}_2+3.78 \mathrm{~N}_2\right)$. The stoichiometric fuel to air mass ratio for this process is

Note: Atomic Weight: $\mathrm{C}(12), \mathrm{H}(1)$

Effective Molecular Weight: Air(28.8)

Ignore any conversion of N 2 in air to the oxides of nitrogen $\left(\mathrm{NO}_{\mathrm{x}}\right)$

The Surface Overflow Rate (SOR) in a rectangular sedimentation tank is $45 \mathrm{~m}^3 / \mathrm{m}^2 / \mathrm{d}$. Minimum diameters of spherical inorganic and organic particles expected to be completely removed in this tank are calculated. Assume that Stoke's law is applicable. Which of the following options is/are correct: Specific gravity of inorganic particles $=2.65$ Specific gravity of organic particles $=1.20$ Acceleration due to gravity $(\mathrm{g})=9.81 \mathrm{~m} / \mathrm{s}^2$ Kinematic viscosity $(v)=1 \times 10^{-6} \mathrm{~m}^2 / \mathrm{s}$

Aeration is employed as a treatment option for the removal of several pollutants from contaminated water. Identify the pollutant(s), where aeration is employed as a part of their removal:

$\mathrm{MgCl}_2$ and $\mathrm{CaSO}_4$ salts are added to 1 litre of distilled deionized water and mixed until completely dissolved. Total Dissolved Solids (TDS) concentration is $500 \mathrm{mg} / \mathrm{l}$, and Total Hardness (TH) is $400 \mathrm{mg} / \mathrm{l}$ (as $\mathrm{CaCO}_3$ ). The amounts of $\mathrm{MgCl}_2$ and $\mathrm{CaSO}_4$ added are calculated (rounded off to the nearest integer). Which of the following options is/are true:

Atomic weights: $\mathrm{Ca}(40), \mathrm{Mg}(24), \mathrm{S}(32), \mathrm{O}(16), \mathrm{Cl}(35.5), \mathrm{C}(12)$