To neutralize completely $20 \ mL$ of $0.1 \ M$ aqueous solution of phosphorous acid $(H_3PO_3)$,the volume of $0.1 \ M$ aqueous $KOH$ solution required is .......... $mL$.

The reduction of boron trichloride $(BCl_3)$ by hydrogen yields elemental boron (atomic mass $10.8 \ g/mol$). If $21.6 \ g$ of boron is produced,what is the volume of hydrogen gas required at $273 \ K$ and $1 \ atm$ pressure (in $L$)?

Given the ratio of masses of nitrogen and oxygen in a particular gaseous mixture is $4: 1$. Calculate the ratio of the number of their molecules.

$9.3 \ g$ of aniline is subjected to reaction with excess of acetic anhydride to prepare acetanilide. The mass of acetanilide produced if the reaction is $100 \%$ completed is $x \times 10^{-1} \ g$. Find the value of $x$. (Given molar mass in $g \ mol^{-1}: N: 14, O: 16, C: 12, H: 1$)

At constant temperature and pressure,the change in volume when $80\%\, 100\, mL$ of phosgene $(COCl_2)$ decomposes into $CO$ and $Cl_2$ is an increase of ............... $mL$.

$A$ $100 \ mL$ solution of $CH_3CH_2MgBr$ on treatment with methanol produces $2.24 \ mL$ of a gas at $STP$. The weight of gas produced is $......mg$. [nearest integer]