When a hydrocarbon $A$ undergoes combustion in the presence of air,it requires $9.5$ equivalents of oxygen and produces $3$ equivalents of water. What is the molecular formula of $A$?

What is the volume (in litres) of oxygen at $STP$ required for complete combustion of $32 \,g$ of $CH_4$? (Molecular weight of $CH_4$ is $16$)

What is the mass of the precipitate formed when $50 \ mL$ of $16.9 \%$ solution of $AgNO_3$ is mixed with $50 \ mL$ of $5.8 \%$ $NaCl$ solution (in $g$)? (Atomic masses: $Ag = 107.8, N = 14, O = 16, Na = 23, Cl = 35.5$)

The volume of water to be added to $100 \, cm^3$ of $0.5 \, N \, H_2SO_4$ to get decinormal concentration is ........ $cm^3$.

In the above reaction,$3.9 \ g$ of benzene on nitration gives $4.92 \ g$ of nitrobenzene. The percentage yield of nitrobenzene in the above reaction is............. $\%$. (Round off to the Nearest Integer).
(Given atomic mass: $C : 12.0 \ u$,$H : 1.0 \ u$,$O : 16.0 \ u$,$N : 14.0 \ u$)

$120 \ g$ of urea are present in $5 \ L$ of solution. The active mass of urea is: