$A$ solution of $CaCl_2$ is $0.5 \, mol/L$. The number of moles of chloride ions in $500 \, mL$ of this solution will be:

$X \ g$ of nitrobenzene on nitration gave $4.2 \ g$ of $m-$dinitrobenzene. $X = ............ \ g$. $(nearest \ integer)$ [Given: molar mass (in $g \ mol^{-1}$) $C: 12, H: 1, O: 16, N: 14$]

Complete combustion of $3 \ g$ of ethane gives $x \times 10^{22}$ molecules of water. The value of $x$ is ......... (Round off to the Nearest Integer). [Use: $N_{A} = 6.023 \times 10^{23} ;$ Atomic masses in $u$ $C = 12.0, O = 16.0, H = 1.0$]

How many $g$ of a dibasic acid (Mol. wt. $= 200$) should be present in $100 \ mL$ of its aqueous solution to give decinormal strength?

One litre of a gas at $STP$ weighs $1.16 \ g$. It can possibly be:

Combustion of $10 \ mL$ of a gaseous hydrocarbon gives $40 \ mL$ of $CO_2$ and $50 \ mL$ of water vapour under the same conditions. The molecular formula of the hydrocarbon is